Chemistry

What's the difference between a double-displacement reaction and a neutralization reaction?

A double displacement reaction (aka metathesis rxn) happens when elements from 2 different compounds swap places to form 2 new compounds (e.g. CaCl2 + 2AgNO3 -> Ca(NO3)2 + 2AgCl A neutralizaiton reaction is a special type of double displacement rxn where an acid reacts with a base to produce salt and usually water - e.g. HCl + NaOH -> NaCl + H2O

Why does IUPAC not consider Zn(s) a transition metal?

A transition metal is an element whose atom has an incomplete d subshell or which can give rise to cations with an incomplete d subshell. Zinc has a full d orbital in both its natural state and ionic state, as it gives up 4s subshell electrons to become a divalent cation.

Carbon 14 is very unstable and decays by releasing a beta particle, becoming a nitrogen atom. C-14 has a half life of 5,470 years - interpret this for two half lives in a 10g starting sample.

After 5,470 years, there would be a 50% chance of any of the carbon-14 atoms in the sample having become nitrogen-14 atoms by beta decay. If there were 10 grams of carbon, after one half life, about 5g would have decayed into nitrogen; after two, ~7.5g would have decayed into nitrogen with ~2.5g remnant C-14.

What is the main characteristic of transition metals?

An element whose atom has an incomplete d subshell or which can give rise to cations with an incomplete d subshell.

Compare the Aufbau Principle, the Pauli Exclusion Principle, and Hund's Rule.

Aufbau Principle is the "building up" principle, which states that electrons will fill in lower energy orbitals first. The Pauli Exclusion Principle is the "unique address" principle, which states that no two electrons can have the same four quantum numbers. Hund's Rule is the "empty seat bus" rule, which states that electrons will fill in orbitals one at a time before pairing up.

If Hydrogen and Lithium both have the same Zeff, why does Hydrogen have a higher ionization energy?

Because Lithium's outer electron is farther away from the nucleus. Ionization energy hence decreases down a group, despite constant Zeff.

Why doesn't Hydrogen produce a continuous spectrum of light?

Because its orbitals have specific energy difference between them, resulting in light waves with specific energy levels and thus specific wavelengths. It cannot produce every different wavelength level.

Describe the relationship between energy of photon with respect to the wavelength emitted by an electron

E(photon) = hv c = ƛv v = c/ƛ E = h*c/ƛ (h = Planck's constant; c = speed of light; E = energy) hc/ƛ = E1 - E2 (E1 is the high energy state; E2 is the low)

Energy can become mass, and mass can become energy. What is the equation behind this energy-mass equivalence phenomenon?

E=mc^2 Therefore, binding energy can be measured in Joules or amu

Electron affinity trends on a periodic table

EA - opposite concept of IE - energy release upon accepting an electron in the form of heat (exothermic). The greater the Zeff (electrostatic pull), the more energy released = higher EA. Hence, EA increases along a period and decreases down a group. Group 1 and 2 metals have the lowest EA's while the halogens have the greatest.

Which is a stronger base, H2O or Cl-, in the following reaction: H2O + HCl <-> H3O+ + Cl-

H2O is a stronger base than Cl- because Cl- is the conjugate base of a strong acid, making it a very weak base.

Acids and bases may react with each other to form a salt and often (not always), water. What is this type of reaction called? How about the reverse reaction?

HA (aq) + BOH (aq) --> BA (s) + H2O (l) This is a neutralization reaction, a special type of double displacement chemical reaction. The reverse, in which salt ions react with water to give back the acid or base, is known as hydrolysis.

What is the Heisenberg uncertainty principle?

Heisenberg uncertainty principle = it is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron. The more accurately you know the position of a particle, the less accurately you know the momentum of it.

An alpha particle in alpha decay has the same nuclear composition as which element?

Helium. In alpha decay, a nucleus ejects an alpha particle (which has 2p and 2n) and the remnant - both charge and nucleons are retained.

If you had ~73% Hg and 27% Cl in a bag, how can you determine the molecular formula of the molecule?

HgCl2 is the formula. Using molar mass, you can determine the number of moles and take it from there.

A substance with a hydration complex (complex metal ions in solution that associate with water molecules) gives off a red colour. We know that the colour given off is the colour that was not absorbed, and thus we perceive a complementary colour of the absorbed frequency. What is the colour of the absorbed frequency? (A) Green (B) Cyan (C) Yellow

(B) Cyan Complementary colours are as such: red/cyan, green/magenta, blue/yellow. Many complexes absorb frequencies of light needed to 'jump' electrons to energy states in higher d-orbitals - the frequencies not absorbed provide the colour.

Carbon (electronegativity of 2.5) bound to Oxygen (electronegativity of 3.5) is what type of bond? How did you know this based on electronegativity values? (A) Nonpolar covalent (B) Polar covalent (C) Ionic (D) Hydrogen

(B) Polar covalent Carbon and Oxygen have an electronegativity difference of 1.0, which is greater than .5, making their bond a polar covalent bond.

You have a substance that is composed of 20.8% Iron and 79.2% Chlorine by mass. What is the chemical formula of this compound (periodic table: http://www.chem.qmul.ac.uk/iupac/AtWt/table.gif)? (A) FeCl3 (B) Fe2Cl3 (C) FeCl6 (D) Fe3Cl6

(C) FeCl6 Pretend you have 20.8 g of Fe. That would be 20.8 g / 55.845 g -> approx. .33 moles Fe Pretend you have 79.2 g Cl. That would be 79.2 g / 35.45 g -> approx. 2 moles Cl. So, for every 1 Fe atom, you must have 6 atoms of Cl, making the formula FeCl6.

Sodium (electronegativity of .9) bound to Chlorine (electronegativity of 3.0) is what type of bond? How did you know this based on electronegativity values? (A) Nonpolar covalent (B) Polar covalent (C) Ionic (D) Hydrogen

(C) Ionic Sodium and Chlorine have an electronegativity difference of 2.1, which is greater than 1.7, making their bond an ionic bond.

The actual mass of a Helium atom is 0.03amu less than its predicted mass (the sum of individual masses of its subatomic particles). In the case of helium, 0.03amu is considered: (A) Binding energy (B) Atomic energy (C) Mass defect (D) Atomic mass

(C) Mass defect The mass defect is the difference in the actual and predicted masses of atoms, and is due to loss of mass due to binding energy

Metals are solids at room temperature. The only exception is which metal element? (A) Bromine (B) Cobalt (C) Mercury (D) Manganese

(C) Mercury - liquid at room temperature

Carbon is an example of which type of substance? (A) Diamagnetic (B) Antiferromagnetic (C) Paramagnetic (D) Ferromagnetic

(C) Paramagnetic Carbon is an example of a paramagnetic substance because its outermost orbital has unpaired eletrons.

Which type of substance will be pulled into an external magnetic field? (A) Diamagnetic (B) Antiferromagnetic (C) Paramagnetic (D) Ferromagnetic

(C) Paramegnetic

What is the pH of a 4.65⋅10^-4 M solution of acetic acid (Ka = 1.8⋅10^-5)? (A) 7.86 (B) 6.02 (C) 4.89 (D) 4.08

(D) 4.08 Ka = ([CH3COO-][H3O+])/[CH3COOH] 1.8⋅10^-5 = x^2/4.65⋅10^-4 - x (but x is so little that we can disregard it), making our equation: 1.8⋅10^-5 = x^2/4.65⋅10^-4 (1.8⋅10^-5)(4.65⋅10^-4) = x^2 approx. 90⋅10^-10 = x^2 approx. 1⋅10^-4 = x pH = -log(1⋅10^-4) pH = approx. 4 (actual: 4.08)

Describe the following types of chemical reactions: 1) combination rxn 2) decomposition rxn 3) combustion rxn 4) single-displacement rxn

1) Combination reaction - 2 or more reactants form one product (e.g. 2H2 + O2 -> H2O) 2) Decomposition reaction - opposite of combination reaction - a single reactant forms two or more products (2HgO --> 2Hg + O2) 3) Combustion reaction - special type of rxn involving a fuel (usually a hydrocarbon) and an oxidant (usually O) - most common, reactant forms two products of CO2 and water (e.g. combustion of methane CH4 -> CO2 + H2O) 4) Single-displacement reaction - when an atom/ion in a compound is replaced by an atom/ion of another element - e.g. solid copper metal displacing silver ions in clear solution of silver nitrate to form blue copper nitrate and silver metal (Cu + AgNO3 -> Ag + CuNO3)

Why does size increases as you go down a group? Why does size decrease as you go left to right on a period?

1) Size increases as you go down a group due to adding of electron shells/energy levels. 2) Size decreases along a period (left to right) because outer electrons lie in the same valence shell, but increase in atomic number means increase in effective nuclear charge (Zeff), which leads to greater attraction of electrons to the nucleus.

A given unstable isotope has a decay constant = 0.1y^-1 (y=years). (1) Find the half life of this isotope; (2) if we begin with a 100g sample, how much is left over after 25 years?

(1) 6.93 years; (2) 8.21 grams

What is the Rydberg equation, which relates wavelength of light emitted to the orbital level change of an electron?

(1/λ) =R((1/nf^2) - (1/ni^2)) λ = Wavelength R = Rydberg's Constant (1.097⋅10^7) nf = Final Orbital Level ni = Initial Orbital Level

Na+ is an example of which type of substance? (A) Diamagnetic (B) Antiferromagnetic (C) Paramagnetic (D) Ferromagnetic

(A) Diamagnetic Na+ is an example of a diamagnetic substance because it has paired electrons in its outermost orbital.

Which type of substance will be slightly repelled by an external magnetic field? (A) Diamagnetic (B) Antiferromagnetic (C) Paramagnetic (D) Ferromagnetic

(A) Diamagnetic. Diamagnetic substances will be slightly repelled by an external magnetic field. Diamagnetic substances have only paired electrons in its outermost orbital.

Carbon (electronegativity of 2.5) bound to Hydrogen (electronegativity of 2.1) is what type of bond? How did you know this based on electronegativity values? (A) Nonpolar covalent (B) Polar covalent (C) Ionic (D) Hydrogen

(A) Nonpolar covalent Carbon and hydrogen have an electronegativity difference of .4, which is less than .5, making their bond a nonpolar covalent bond.

An electron within Hydrogen jumps from the second orbital to the first orbital. What wavelength of light is emitted considering that Rydberg's constant is 1.097⋅10^7? (A) 6.78⋅10^-4 (B) 1.22⋅10^-7 (C) 1.81⋅10^-9 (D) 8.43⋅10^-15

(B) 1.22⋅10^-7 (1/λ) =R((1/nf^2) - (1/ni^2)) (1/λ) =(1.097⋅10^7)((1/1^2) - (1/2^2)) (1/λ) = approx. (.75⋅10^7) 1/(.75⋅10^7) = λ 1.34⋅10^-7 = λ, which is closest to (B) 1.22⋅10^-7

The half-life for C-11 is 20 minutes. If we start with 100g, how many grams of C-11 will be left over after 60 minutes? (A) 50g (B) 12.5g (C) 25g (D) 0g

(B) 12.5g 100g -(20min)-> 50g -(40)-> 25g -(60)-> 12.5g Half life is the amount of time it takes for a certain substance to fall half its amount.

Which of the following is true of beta decay? (A) The beta particle is a neutrino (B) A neutron becomes a proton (C) There's an increase/decrease in the number of nucleons (D) The number of neutrons is conserved

(B) A neutron becomes a proton. This is a simplified understanding, but in beta decay, the ejection of a beta particle (an electron) causes a change in overall charge due to loss of a negative charge. Process leads to conversion of a neutron (neutral) to a proton (+). n --> p + e + v (v is an anti-neutrino) The neutron becomes a proton by releasing an electron (the beta particle)

What is the limiting reagent in the following reaction conditions with 7 moles A, 10 moles C and 2 moles AC2, and given the reaction: 1 mol A + 2 mol C -> 1 mol AC2 (A) A Only (B) C Only (C) AC2 Only (D) A and C

(B) C Only If 7 mol of A are available and 1 mol of A is needed to form 1 mole of product, it could form up to 7 mol of AC2. If 10 mol of C are available and 2 mol C are needed to form 1 mol product, then up to 5 mol of AC2 could be produced. Thus, C is the limiting reagent. Because AC2 is not a reagent, it can be excluded.

Which of the following is the strongest base? (A) F- (B) CH3O- (C) CH3COO- (D) NO3-

(B) CH3O- CH3OH is a very weak acid, so its conjugate base will be extremely strong. Likewise, the conjugate acid of a weak base will be very strong, and the conjugate base of a strong acid/conjugate acid of a strong base will be weak

A cation is bigger or smaller than its original atom? Why?

Smaller because you are taking an electron away, potentially reducing electron repulsion, making it smaller.

Ka >> 1. What does this entail?

Strong acids and bases dissociate completely into their constituents. So for acids, they would donate protons very easily, and the reaction would be able to go through about 100%. H2O + HCl -> H3O+ + Cl- Ka = [H+][Cl-]/[HCl] The stronger an acid, the weaker it's conjugate base. For the reaction above, it holds true because water is a much stronger base than the chloride anion. On the other hand, for a weak acid rxn like with acetic acid: CH3COOH + H2O <---> H3O+ + CH3COO- The Ka value (Ionization constant) is much smaller than 1 (Ka<<1) - acetic acid stays mostly protonated.

Differentiate between the Bohr model and Quantum mechanical model of an atom - which is right?

The Bohr model states that electrons orbit the nucleus, like planets around the sun - it serves as a useful model to understand the concept. However, the correct model is the quantum mechanical model which states that electrons are in orbitals and not fixed in orbits - we would be unlikely to know the exact position of an electron at a given time, but know what orbital and pattern it would move in.

There are 2 notable exceptions seen to electron configuration rules - chromium and copper. The electron configuration for Chromium can be written as [Ar] 4s^1 3d^5 (when it would expectedly be 4s^2 3d^4), while copper can be written as [Ar] 4s^1 3d^10 (instead of 4s^2 3d^9). What is the reason for the inconsistency of electron conf. rules with these elements?

The concept behind this is that half-filled and fully filled orbitals have lower energy (and therefore higher stability) than other states. This is accomplished in these cases for chromium (half filled 3d orbital) and copper (filled 3d orbital) by moving an electron from the 4s subshell into the 3d subshell. Though it would normally be energetically unfavourable to transfer the electron as such, the overall lower energy and more stable state compensates for this in such cases. Other elements can also experience similar shifts with f subshells, but never with p subshells (extra stability doesn't outweigh energetic cost)

Why is it that transition metals can form different possible charged atoms (oxidation states)?

They are capable of losing a different number electrons from s or d orbitals - thus, many metals can form different ionic compounds.

True or false: a type of radioactive decay is when an atom "captures" an electron and combines it with a proton to form a neutron.

True - this is called electron capture.

True of False? The ability to know the position and the ability to know the momentum of a moving particle are inversely related.

True. The ability to know the position and the ability to know the momentum of a moving particle are inversely related. As the knowledge of one increases, knowledge of the other decreases.

What are the possible values of n, l, m(l), and m(s) for when n= 3? How many electrons are in this shell?

n = 3 l = 0, 1, or 2 (s, p, or d) m(l) = -2, -1, 0, or +1, +2 m(s) = + (up) or - (down) # of electrons = 18

Calculating pH and/or [H3O+]

pH = -log[H3O+] -pH = log[H3O+] [H3O+] = 10^-pH

Calculate the pH of an aqueous ammonia solution with a [OH-] of 2.1 * 10^-3 M.

pH = 11.32

Determine the pH of a 0.500M solution of ammonia (NH3).

pH = 11.48

Calculate the pH of an aqueous solution with 0.11g Ca(OH)2 in a total volume of 250ml

pH = 12.08

What equation tells you the number of possible stereoisomers?

#SI = 2^n #SI = # of stereoisomers n = number of stereocenters.

Calculate the heat of formation for the following reaction: 8 Al(s) + 3 Fe3O4(s) → 4 Al2O3(s) + 9 Fe(s) ΔH for Fe3O4(s) = -1120.9 kJ/mol ΔH for Al2O3(s) = -1669.8 kJ/mol (A) -3,316.5 kJ (B) -2,563.6 kJ (C) -1,657.2 kJ (D) -53.9 kJ

(A) -3316.5kJ (4*-~1700) - (3*~-1100) = -6800 + 3300 = ~ -3500

What is the Kb of Cl- if the pKa of Cl- is -7? (A) 1⋅10^-21 (B) 1⋅10^-14 (C) 1⋅10^-7 (D) 1⋅10^7

(A) 1.10*10^-21 pKb = -log(Kb) 21 = -log(Kb) Kb = 1⋅10^-21

In gel electrophoresis, the cathode produces a ___________ charge while the anode produces a ___________ charge. (A) negative, positive (B) positive, neutral (C) neutral, negative (D) positive, negative

(A) negative, positive Reduction takes place at the cathode. Those lost electrons then travel toward the positively charged anode, which is where oxidation (gain of electrons) takes place.

PbCl2 (Ksp = 1.60⋅10^-5) is added to a 8.79⋅10^-2 M solution of KCl. What is the final concentration of Pb2+? (A) .00021 M (B) .0021 M (C) .021 M (D) .21 M

(B) 0.0021M. PbCl2 --> Pb2+ + 2Cl- Decrease in PbCl2 by x = increase in Pb2+ by x and Cl- by 2x (because 2x Cl- for each 1 PbCl2) thus, [Pb2+] = x initial concentration of Cl = [KCl] = ~9*10^-2 thus, [Cl-] after addition is 9*10^-2 + 2x Ksp = [Pb2+]*[Cl-] = 1.6*10^-5 =~2*10^-5 2*10^-5 = [x]*[9*10^-2 + 2x]^2... if x<<1, then 2x is negligible and ~=0 [x] = (2*10^-5)/(9*10^-2)2 = (2*10^-5)/(81*10^-4) x = 2/81 * 10^-1 = ~0.02*10^-1 = .002

What is the pH when you have a [OH-] concentration equal to 9.84⋅10^-8 M? (A) 8.67 (B) 7.92 (C) 6.99 (D) 5.43

(C) 6.99

Describe what happens in gas chromatograph in terms of: - Nature of the stationary phase - Solubility of the gas - Length of the column - Temperature in column - Flow rate of the mobile phase

- *Nature of the stationary phase*: if there is strong attraction between the gas and liquid stationary phase, gas spends more time bonding to it and retention time will increase - *Solubility of the gas*: more soluble the gas, more time spent dissolving in liquid = increased retention time - *Length of the column*: a longer column = gas spends more time in the column = increased retention time, as well as increased resolution of bands produced (they will be farther apart) - *Temperature in column*: increasing the temperature inside means the solubility of the gas will decrease (because kinetic energy increases) and it will travel faster through the liquid phase = decreased retention time - *Flow rate of the mobile phase*: increasing the rate the carrier gas moves thereby increases the rate at which mixture moves = decreased retention time

Relationship between grams and moles?

1 gram = 1 mole of amu's = 6.022*10^23 amu's 1 g H = 1 mol H

What is the difference between acids and bases based on: 1) Arrhenius definitions 2) Bronsted Lowry definitions 3) Lewis definitions

1) Arrhenius definitions - an Arrhenius acid will dissociate to form excess H+ in solution; an Arrhenius base will dissociate to form excess OH- in solution 2) Bronsted Lowry is proton based. Acids are proton donors (H+ donor), while bases are proton acceptors. Bronsted Lowry acids and bases always occur in pairs because of the required transfer of a proton from an acid to a base - conjugate acid-base pairs 3) Lewis is electron based. A Lewis acid is an electron pair acceptor, while base is an e- pair donor.

Describe the expected products from the four combinations of acid-base reactions: 1) strong acid + strong base 2) strong acid + weak base 3) weak acid + strong base 4) weak acid + weak base

1) strong acid and strong base - reaction will result in equimolar amounts of "neutral" salt and water (if conc of acid and base are also equimolar) e.g. HCl + NaOH --> NaCl + H2O 2) strong acid + weak base - products will also be salt but usually no water, as weak bases do not have hydroxides - "acidic" salt e.g. HCl + NH3 --> NH4Cl 3) weak acid + strong base - initial pH of higher than 7 due to many hydroxide ions present - shifts equilibrium away from autoionization and hence formation of too many H3O+. The reaction will form a salt and water. Forms a "basic" salt. e.g. HClO + NaOH --> NaClO + H2O e.g. CH3COOH + NaOH --> CH3COO-Na+ + H2O 4) weak acid + weak base - the pH will depend on the relative strengths of the WA and WB. For the example reaction HClO + NH3 --> NH4ClO, the pH of solution will be more basic at equilibrium because NH3 has a higher Kb (1.8*10^-5) than HClO's Ka (3.2*10^-8).

Calculate the pH of a solution that is 0.15M NH3 (Kb = 1.8*10^-5) and 0.35M NH4NO3.

1.8*10^-5 = 0.35x/0.15 (with the same assumption that x << 1) x = 7.7*10^-6 M = [OH-] pOH = -log[OH-] = -log (7.7*10^-6) = pOH = 5.11 pH = 14 - pOH = 8.89

What is a buffer solution?

A buffer solution has a mix of a weak acid and its salt (which is composed of its conj. base and a cation) OR a mix of a weak base and its salt (its conj. acid and an anion). Examples: solution of acetic acid (CH3COOH) and it's salt (CH3COO-Na+), an acid buffer, and solution of ammonia (NH3) and its salt (NH4+Cl-), a base buffer. Buffer solutions have useful property of resisting changes in pH when small amounts of acid or base are added.

What does optical activity refer to?

A compound if optically active if it can rotate plane-polarized light (due to a chiral molecule)

Differentiate between the absorption and emission

Absorption is when an atom's electron in the ground state (lowest energy state/shell, n=1) absorbs energy and "jumps" to a higher energy level (excited state). Emission is when the electron returns to the low energy state from high and emits a photon with certain wavelength - the energy of the photon is equal to the difference between the two energy levels (high and low).

Do questions 1 through 15 to test yourself on your ability to distinguish enantiomers from diasteriomers: http://www.susanhornbuckle.com/CHEM2411/Study%20Aides/Enantiomers%20diastereomers%20self%20test/Enantiomers%20diastereomers%20or%20same%20self%20test.htm

Answers can be found on the same webpage: http://www.susanhornbuckle.com/CHEM2411/Study%20Aides/Enantiomers%20diastereomers%20self%20test/Enantiomers%20diastereomers%20or%20same%20self%20test.htm

When do you assign the Z designation to an alkene? E designation?

Assign the Z designation when the high-priority groups are on the same side (Zame) Assign the E designation when the high-priority groups are on opposite sides (oppositE)

Draw a generic Phospholipid.

Basically a Triglyceride with a Phosphate group.

Balance the following chemical equation: C6H12O6 + O2 -> CO2 + H2O

C6H12O6 + 6O2 -> 6CO2 + 6H2O

Compare the polarity of CCl4 and CHCl3. Why is the polarity the same/different?

CCl4 is non-polar due to its symetrical structure. CHCl3 is polar due to its non-symetrical structure.

What is the Electron Geometry of BrF3? Molecular Geometry?

Electron Geometry of BrF3 is Trigonal Bipyramidal. Molecular Geometry of BrF3 is T-shaped.

What is the Electron Geometry of BrF5? Molecular Geometry?

Electron Geometry of BrF5 is Octahedral. Molecular Geometry of BrF5 is Square Pyramidal.

What is the Electron Geometry of Carbonate? Molecular Geometry?

Electron Geometry of Carbonate is Trigonal Planar. Molecular Geometry of Carbonate is Trigonal Planar.

What is the Electron Geometry of ClF3? Molecular Geometry?

Electron Geometry of ClF3 is Trigonal Bipyramidal. Molecular Geometry of ClF3 is T-shaped.

What is the Electron Geometry of H2O? Molecular Geometry?

Electron Geometry of H2O is Tetrahedral. Molecular Geometry of H2O is Bent.

What is the Electron Geometry of H3O+? Molecular Geometry?

Electron Geometry of H3O+ is Tetrahedral. Molecular Geometry of H3O+ is Trigonal Pyramidal.

What is the Electron Geometry of I3-? Molecular Geometry?

Electron Geometry of I3- is Trigonal Bipyramidal. Molecular Geometry of I3- is Linear.

What is the Electron Geometry of SF6? Molecular Geometry?

Electron Geometry of SF6 is Octahedral. Molecular Geometry of SF6 is Octahedral.

True or False? A change in entropy for a reaction that is greater than 0 for a reaction, implies that the reaction went from a less ordered state to a more ordered state.

False. A change in entropy for a reaction that is greater than 0 for a reaction, implies that the reaction went from a more ordered state to a less ordered state. Entropy is a measure of DISorder.

True or false: for a molecule to have optical activity, only chiral centers are required.

False. A molecule must have not only chiral centers, but also must lack a plane of symmetry. If the plane of symmetry exists, the molecule is not optically active regardless of possessing chiral centers.

True or False. Due to their metallic properties, metalloids are considered conductors just as metals are.

False. Metalloids are considered semi-conductors.

True or False? Sugars that are Hemiacetals are terms Glycosides.

False. Sugars that are ACETALS are terms Glycosides.

True or False? The larger the Ka value, the weaker the acid.

False. The larger the Ka value, the STRONGER the acid.

True or false: High ionization energy is directly proportional to electronegativity for ALL elements on the periodic table

False. This rule is generally true but exceptions are the noble (inert) gases, which have the highest ionization energies but no electronegativity because they do not form bonds in nature.

True or false: a hydrocarbon will dissolve in a polar aprotic solvent such as water.

False: They cannot H bond and are not polar, thus will not dissolve in polar solvents. "polar dissolves polar, nonpolar dissolves nonpolar" - so hydrocarbons would mix readily in a nonpolar solvent of hydrocarbons.

How many valence electrons does Flourine have?

Flourine has 7 valence electrons.

Does Gel Electrophoresis utilize an electrolytic or a galvanic cell?

Gel Electrophoresis utilizes an electrolytic cell. It is using energy to drive a non-spontaneous reaction (i.e. the movement of the proteins or DNA in the gel).

Strong bases are formed from which two groups of the periodic table mixed with OH?

Groups 1A and 2A (alkali metals and alkaline earth metals)

What is Le Chatelier's principle?

If you increase the concentration of one of your products, the equilibrium shifts towards the left.

Ka and Kb are related, how?

Ka * Kb = Kw

What are the pH ranges for the indicators?

Methyl red (4.4-6.2) Bromthymol blue (6-7.6) Phenolphthalein (8.2-10) For SA/SB titration, any of the three could be used due to the steep titration curve. For WA/SB where the pH>7 for the equivalence point (because the conjugate base reacts with water to increase [OH-]), phenolphthalein would be ideal. For WB/SB the pH of the equivalence point is <7 (if you reacted all weak base with strong acid, you're protonating your weak base - left with NH4+ - increases [H+] aka [H3O+]) - ideal indicator is methyl red (4.4-6.2).

What are the formulae for permanganate and cyanide anions?

MnO4- (permanganate) CN- (cyanide)

P4 + 6 Cl2 --> 4 PCl3 If you have 1.45g of P4, how many grams of Cl2 are required, and how much PCl3 is produced?

Molc weight of P = 31g; thus, weight of mole of P4 is 124g. 1.45g of P4 is 0.0117 moles. Thus, 6*0.0117 = 0.07 mol of Cl2 required - 35.453*2 (2 Cls) = 70.9g/mol * 0.07mol = 4.96g Cl2.

Monosaccharides are the most basic form of carbohydrates. Monosacchs with three carbon atoms are called ______________; with four, five and six C's are called ___________, _____________, _____________ respectively.

Monosaccharides are the most basic form of carbohydrates. Monosacchs with three carbon atoms are called *trioses*; with four, five and six C's are called *tetroses*, *pentoses*, hexoses* respectively.

What are the formulae for nitrate and nitrite anions?

NO3- (nitrate) NO2- (nitrite)

What are the formulae for peroxide and oxalate anions?

O2^2- (peroxide) C2O4^2- (oxalate)

What are prostaglandins?

Prostaglandins are 20-C molecules that are unsaturated carboxylic acids derived from anarchidonic acid - they are autocrine and paracine signals that regulate synthesis of cAMP and have downstream effects associated with increased body temp, fever and pain.

What is the equation for specific rotation?

Rotation is experimentally determined and the amount depends on the number of molecules that a light wave encounters - two factors are concentration of optically active compound and length of the tube through which light passes. *[α] = (α obs)/c x l* α = specific rotation in degrees α obs = observed rotation in degrees c = concentration in g/ml l = path length in dm (1dm = 10cm)

What are the formulae for thiosulfate and thiocyanate anions?

S2O3^2- (thiosulfate) SCN- (thiocyanate)

The _________ Formula of Glucose is C6H12O6 while the _________ Formula of Glucose is CH2O. Fill in the blanks using the following options: - Empirical - Atomic - Molecular - Compound

The Molecular Formula of Glucose is C6H12O6 while the Empirical Formula of Glucose is CH2O.

Explain the relationship between an acid-base indicator (like phenolphthalein) and the end point of a titration?

The acid-base indicator will have specific pH where it changes color (phenolphthalein is colorless in acidic conditions and pink in basic conditions). At the end point of the titration, the acid-base indicator changes colors, showing that just enough reactant has been added to eliminate the acidic/basic conditions.

Draw an Anti vs. Gauche Newman Projection

The anti conformation is the other type of staggered conformation where the two largest substituents are antiperiplanar (on the same plane but opposite sides) - it is the most energetically favourable arrangement. To convert from anti to gauche conformation, the molecule must pass through the eclipsed conformation (angle 120 degrees). Totally eclipsed is when the angle is 0 degrees.

What would happen if your sands/beads ended up slanted while doing a Column Chromatography?

The bands would mix and the compounds would not separate appropriately.

The next step is to decide on the central atom. Which should be the central atom for SiF4 and why?

The central atom for SiF4 should be Si because it is the least electronegative as compared to F.

What is the common ion effect?

The common ion effect states that if the concentration of any one of the ions is increased, then by Le Chatelier's principle, some of the ions will be removed from solution by combining with oppositely charged ions, until equilibrium is reached.

How does the common ion effect relate to solubility?

The common ion effect will decrease solubility as it will push the reaction in the reverse direction.

Why does electron affinity increase as you go up a group? Why does electron affinity increase as you go to the right on a period?

The electron affinity increase as you go up a group because the atom is getting smaller, which means the electron is being added closer to the positively charged nucleus. The electron affinity increases as you go to the right on a period because of increased nuclear charge with the same amount of shielding.

Describe the equivalence point.

The equivalence point is where just enough of your standard solution has been added to completely react with the solution being titrated. At the equivalence point, the number of equivalents of acid and base are equal - this allows us to calculate the unknown concentration of the titrant via the equation: MaVa = MbVb (Ma = molarity of acid; Mb = molarity of base; Va and Vb = volume of acid and base respectively).

You add water to a solution of isobutyric acid and diethyl ether and place them into the Seperatory Funnel. Which would be considered the aqueous and which would be considered the organic layer? Which would end up on top and which would end up on bottom?

The isobutyric acid will transfer to the water layer to form the *aqueous phase (layer)* and the nonpolar ether layer will form the *organic phase (layer)*. Isobutyric acid mixes with water due to polarity of COOH group

You have 32 grams of NH3 and O2 each. For the following reaction, determine which of the two reactants is the limiting reagent: 4 NH3 + 5 O2 --> 4 NO + 6 H2O

The limiting reagent is oxygen. You come to find that 32g is equal to 2 moles of NH3 but only one mole of O2 - thus, with 1 mole of O2 only 0.8mol of NH3 will be able to react, with the rest being remnant. Thus, O2 is the limiting reagent.

The second step in assigning R and S designations is to arrange what group projecting away?

The lowest priority group.

If you add 0.005mol NaOH to 0.5L of the same solution (0.24M NH3 and 0.20M NH4Cl, pH 9.33), what becomes the new pH?

The new pH = 9.37 - demonstrates how a buffer solution resists pH change.

True or false: because SN1 rxns pass through a planar intermediate before the nucleophile attacks, the product will be a racemic mixture of left- and right-handed enantiomers.

True.

True or False. All spontaneous reactions are irreversible.

True. All spontaneous reactions are irreversible, and would require input of energy to go in the reverse direction.

True or false: the more number of moles/particles in a system, the more enthalpy.

True. Enthalpy is related to the internal energy of the system (ΔU) - thus the more of a system, the more enthalpy.

True or false? Hess's Law states that the energy change of a process is independent of the path that was taken to get there

True. Hess's Law states that the energy change of a process is independent of the path that was taken to get there

How is D- vs. L- designation determined for sugar molecules?

You look at the final chiral carbon and determine if it is R or S. R -> D. S -> L.

What simple equation illustrates the relationship between effective nuclear charge (Zeff) and electron shielding?

Zeff = Z - S Z = nuclear charge S = electron shielding

In a titration, 27.4ml of a 0.0154M Ba(OH)2 solution is needed to neutralize 20ml of HCl. What is the acid concentration?

[HCl] = 0.0422M. Ba(OH)2 = 0.0154M= x/0.0274L = x = 0.000422mol 1 Ba(OH)2 + 2 HCl --> 2H2O + BaCl2 Ba(OH)2:HCl = 1:2 thus mol of HCl = 0.000422*2 = 0.000844 0.000844/0.02L = [HCl] = .0422M Note: to use MV=MV you'd need to take the answer x2 because of the balanced equation.

Why is the chloride anion larger than the neutral atom?

because adding an electron potentially increases electron repulsion, making it larger.

Describe the relationship between pH and pOH

pH = -log[H+] = log 1/[H+] pOH = -log[OH-] = log 1/[OH-] pH + pOH = 14

State and explain the equation for Gibbs Free Energy.

ΔG = ΔH - TΔS (..where ΔH is the change in enthalpy, T is temperature in Kelvin, and S is a measure of entropy/disorder) Note how temperature is a factor. If temperature is high enough and ΔS<0, then the entire term becomes positive and dominates. This makes sense, as high temperature = input of heat and the reaction no longer being spontaneous.

When is ΔG spontaneous?

ΔG > 0 = not spontaneous ΔG < 0 = spontaneous

State and explain the formula used to define enthalpy.

ΔH = ΔU + PΔV (where ΔU = internal energy of system; PΔV = work done to displace the environment in creating the current state of the system). Enthalpy is not an intuitive property and cannot be measured like temperature etc. It is a state function and an external property (depends on amount of the system)

How do you calculate heat of formation in a reaction?

ΔHrxn = ΔHproducts - ΔHreactants

What is the difference between α and [α]?

α is the observed rotation and is affected by concentration and path length. For convenience sake, α obs was written to refer to observed rotation. [α] is the absolute rotation and is independent of concentration and path length. A substance's absolute rotation is constant and does not change.

In α- vs. β-glucose, how do you determine whether a sugar is α- vs. β-?

α-sugars have the OH group in the trans conformation as compared with the final carbon. β-sugars have the OH group in the cis conformation as compared with the final carbon.

What is the equation for dipole moment (μ)?

μ = q d μ = Dipole Moment q = Charge d = Distance

Next you need to add up the total number of valence electrons. How many total valence electrons does SiF4 have?

(7x4) + 4 = 32

Consider the following unbalanced reaction that results from titrating a 24.3 mL solution of Fe2+ with 67.9 mL of a 5.63⋅10^-3 M solution of KMnO4: MnO4- + Fe2+ -> Mn2+ + Fe3+ What is the concentration of the original Fe2+ solution? (A) .0786 M (B) .0324 M (C) .9425 M (D) .3652 M

(A) .0786 M First, balance the reaction as follows: MnO4- + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H2O 67.9 mL MnO4- ⋅ 1 L / 1000 mL ⋅ 5.63⋅10^-3 moles MnO4- / 1 L MnO4- = approx. 385⋅10^-6 moles MnO4- (actual: 382.277⋅10^-6) 385⋅10^-6 moles MnO4- ⋅ 5 moles Fe2+ / 1 mole MnO4- = approx. 2000⋅10^-6 moles Fe2+ (actual: 1911⋅10^-6) 2⋅10^-3 moles Fe2+ / 2.43⋅10^-2 L Fe2+ = approx. 1⋅10^-1 M (actual: .786⋅10^-1)

Cl- and H+ have partial charges of -4.76⋅10^-34 C and 4.76⋅10^-34 C, respectively. they are separated by a distance of 2.21⋅10^28 m. What is the dipole moment for HCl based on these numbers? (A) 1.05⋅10^-5 (B) 4.62⋅10^-6 (C) 3.98⋅10^-7 (D) 9.45⋅10^-8

(A) 1.05⋅10^-5 μ = q d μ = (4.76⋅10^-34 C)(2.21⋅10^28 m) μ = approx. 10⋅10^-6 (actual: 10.52⋅10^-6)

(+)-Glyceraldehyde (MM = 90.08) has a specific rotation of 62 degrees. If a 3.2 meter-long polarimeter contains a 143 mL solution containing 4.35⋅10^-3 moles of Glyceraldehyde, what will be the observed rotation? (A) 5.44 (B) 35.84 (C) 78.23 (D) 657.98

(A) 5.44 3.2 meter ⋅ 10 dm / 1 m = 32 dm = l 4.35⋅10^-3 moles ⋅ 90.08 g / mole = approx. 360⋅10^-3 g (actual: 391.848⋅10^-3 g) 360⋅10^-3 g / 143 mL = approx. 2.5⋅10^-3 g/mL (actual: 2.74⋅10^-3 g/mL) [α] = α / (c ⋅ l) 62 = α / (2.7⋅10^-3 ⋅ 32) 62 = α / (90⋅10^-3) 62 ⋅ 90⋅10^-3= α α = approx. 5 (actual: 5.44)

Glyceraldehyde is considered an: (A) Aldotriose (B) Aldotetrose (C) Aldopentose (D) Aldohexose

(A) Aldotriose Glyceraldehyde is considered an aldotriose because it has 3 carbons and contains an aldehyde functional group.

Which of the following is the general structure of a Carbohydrate? (A) Cn(H2O)n (B) Cn(H2O)m (C) Cn(H2O)2n (D) Cn(HO)m

(A) Cn(H2O)n Cn(H2O)n is the general structure of a Carbohydrate.

Which bond is a result of attraction between the oppositely-charged ends of two polar molecules? (A) Dipole-dipole Interaction (B) Hydrogen Bonding (C) London Dispersion Forces (D) Covalent Bonding

(A) Dipole-dipole Interaction A Dipole-dipole Interaction is a result of attraction between the oppositely-charged ends of two polar molecules

Which of the following is NOT true about diastereomers? I. They rotate plane-polarized light in the same magnitude but opposite directions II. They have different chemical and physical properties III. They have multiple stereogenic centers (A) I only (B) I and II only (C) III only (D) I and III only

(A) I only. Diastereomers also rotate plane-polarized light, however knowing the specific rotation of one diastereomer provides no indication of that for the other (stark contrast from enantiomers). The others are true

You are using Gas Chromatography to separate three substances. Line these up from eluting first (left) to eluting last (right): I. Hexanoic Acid II. Hexanone III. Hexane (A) III < II < I (B) III < I < II (C) I < II < III (D) I < III < II

(A) III < II < I In Gas Chromatography, substances are separated based on boiling point, with lower boiling point substances eluting first as is the case here: Hexane (bp = 68° C) < Hexanone (bp = 128° C) < Hexanoic Acid (bp = 401° C)

A molecule with chiral centers and an internal plane of symmetry is called a _____________________. (A) Meso compound (B) Diastereomer (C) Enantiomer (D) Optic chiasm

(A) Meso compound A molecule with chiral centers and an internal plane of symmetry is called a *meso compound*. Meso compounds are essentially the molecular equivalent of a racemic mixture.

The purpose of doing a fractional distillation as opposed to a regular distillation is that a fractional distillation: (A) allows you to separate substances with extremely close boiling points more accurately. (B) allows you to separate substances with extremely distant boiling points more accurately. (C) allows you to separate substances with extremely high boiling points without damaging the substances. (D) allows you to separate substances with extremely low boiling points without damaging the substances.

(A) allows you to separate substances with extremely close boiling points more accurately. The purpose of doing a fractional distillation as opposed to a regular distillation is that a fractional distillation allows you to separate substances with extremely close boiling points more accurately.

The sp3 orbitals of Carbon join with the s orbitals of Hydrogen to make Methane (CH4), forming what type of bonds? (A) σ Bond (B) π Bond (C) α Bond (D) β Bond

(A) σ Bond The sp3 orbitals of Carbon join with the s orbitals of Hydrogen to make Methane (CH4), forming four σ Bonds. All single bonds are sigma bonds. All double bonds have one sigma and one pi bond.

The Mobile Phase travels 8.5 units. compound 1 travels 3.2 units and compound 2 travels 6.4 units. What is the Retention Factor for Compound 1? (A) .22 (B) .38 (C) .50 (D) 2.0

(B) .38 Rf = d (solute) / d (solvent) Rf = 3.2 / 8.5 Rf = approx. .4 (actual: .38)

You have a solution of 78.3 mL of HCl. If it takes 56.2 mL of .143 M Ba(OH)2 to reach the end point of our titration of the HCl solution, what is the concentration of HCl in the original solution? (A) .0205 M (B) .205 M (C) 2.05 M (D) 20.5 M

(B) 0.205 Approximations. Ba(OH)2 + 2HCl --> 2H2O + BaCl2 1 mol Ba(OH)2 = 2 mol HCl - thus, MaVa = MbVb but Ma x2 at the end. MaVa = MbVb = Ma(0.0783 = 0.08L)=(0.143M)(0.0562 = 0.06L) Ma (0.08/0.06) = 0.143M 8/6 = ~1.3 (6*1=6 + 6*0.3=1.8 = 7.8 = ~8) So, Ma (1.3) = (0.143M) = .143/1.3 = ~0.1 0.1*2 = 0.2. (B) is the closest answer.

Calculate Gibb's Free Energy for a reaction in which overall change in Entropy is -24.3 kJ and overall change in Enthalpy is -2354.98 kJ (at a Temperature of 25°C)? (A) 9,596.38 (B) 4,886.42 (C) -4,886.42 (D) -9,596.38

(B) 4,886.42 ΔG = ΔH - TΔS ΔG = -2354.98 - (298K⋅-24.3 kJ) ΔG = -2354.98 - (approx. -7500 kJ (actual: -7,241.4)) ΔG = approx. 5,000 (actual: 4,886.42)

What is the pH of a solution that contains equal concentrations of its conjugate acid and its conjugate base (pKa = 5)? (A) 4 (B) 5 (C) 6 (D) 7

(B) 5 The pH equals the pKa when the concentrations of acid and conjugate base are equal. You did not need the HH equation to solve this.

If the Ka of CH3COOH is 1.8⋅10^-5, what is the pH of a .54 M solution of CH3COO-? (A) 10.35 (B) 9.24 (C) 8.43 (D) 7.21

(B) 9.24 Ka⋅Kb = Kw (1.8⋅10^-5)Kb = 1⋅10^-14 Kb = (1⋅10^-14)/(1.8⋅10^-5) Kb = approx. 5⋅10^-10 (actual: 5.6⋅10^-10) Kb = ([CH3COOH][OH-])/[CH3COO-] 5⋅10^-10 = (x^2)/(.54-x) but we can just assume that x is negligible compared to .54: 5⋅10^-10 = (x^2)/(.54) 2.5⋅10^-10 = x^2 x = [OH-] = approx. 1.35⋅10^-5 (actual: 1.74⋅10^-5) pOH = -log([OH-]) pOH = -log(1.35⋅10^-5) pOH = approx. 4.65 (actual: 4.76) pKw = pOH + pH 14 = 4.65 + pH pH = approx. 9.35 (actual: 9.24)

Waxes are formed via the combination of two molecules with which two functional groups? (A) Alcohol and an Ester (B) Alcohol and a Carboxylic Acid (C) Carboxylic Acid and an Ester (D) Alcohol and an Alcohol

(B) Alcohol and a Carboxylic Acid Waxes (esters) are formed via the combination of two molecules, one having an alcohol functional group and the other (typically a fatty acid) having a carboxylic acid functional group.

Glucose is considered a(n) ______________ and Fructose is considered a(n) _______________. (A) Ketohexose, Aldohexose (B) Aldohexose, Ketohexose (C) Ketohexose, Ketohexose (D) Aldohexose, Aldohexose

(B) Aldohexose, Ketohexose Glucose is considered an aldohexose and Fructose is considered a ketohexose.

Carbohydrates that contain an aldehyde group as their most oxidized functional group are called ______________, where the aldehyde carbon will always be C-1. Those with ketones are their most oxidized FG's are called _____________, where the ketone carbonyl carbon is always C-2. (A) Trioses, ketoses (B) Aldoses, ketoses (C) Pentoses, Hexoses (D) Glyceraldehydes, Ketoses

(B) Aldoses, ketoses Carbohydrates that contain an aldehyde group as their most oxidized functional group are called *aldoses*, where the aldehyde carbon will always be C-1. Those with ketones are their most oxidized FG's are called *ketoses*, where the ketone carbonyl carbon is always C-2. An aldose with 6 C's will be called aldohexose; a ketose with 5 C's will be called ketopentose.

ΔG is negative and ΔH is positive. This means that the reaction is: (A) Exothermic and Spontaneous (B) Endothermic and Spontaneous (C) Exothermic and Non-spontaneous (D) Endothermic and Non-spontaneous

(B) Endothermic and spontaneous. ΔG < 0 = spontaneous ΔH > 0 = endothermic

Which will result in greater separation between bands when running Gas Chromatography? I. Longer Coil II. Higher Temperature III. Higher Pressure (A) I Only (B) I and III Only (C) II and III Only (D) I, II, and III

(B) I and III Only Longer coil, LOWER temperature, and higher pressure will result in greater separation of bands when running Gas Chromatography.

You are using Normal Phase Chromatography to separate an alcohol, an alkane, and a carboxylic acid anhydride. Line these up from eluting first (left) to eluting last (right): I. Alcohol II. Alkane III. Carboxylic Acid Anhydride (A) I < II < III (B) II < I < III (C) III < II < I (D) III < I < II

(B) II < I < III Using Normal Phase Chromatography, the most non-polar substances will elute first; thus, the elution order is as follows: Alkane < Alcohol < Carboxylic Acid Anhydride.

You are using Thin Layer Chromatography to separate three compounds. Line these up from least far (left) to the farthest (right): I. Alcohol II. Alkane III. Carboxylic Acid Anhydride (A) III < II < I (B) III < I < II (C) I < II < III (D) I < III < II

(B) III < I < II In Thin Layer Chromatography, the stationary phase is polar Silica Gel, which will hold on more tightly to polar compounds; thus non-polar compounds will travel the farthest as is the case here: Carboxylic Acid Anhydride < Alcohol < Alkane

The first step in assigning R and S designations is to prioritize the four groups attached to the chirality center. Arrange the following in terms of increasing priority (periodic table: http://www.sbcs.qmul.ac.uk/iupac/AtWt/table.gif): I. Flourine II. Chlorine III. Bromine IV. Hydrogen (A) IV < II < I < III (B) IV < I < II < III (C) III < I < II < IV (D) III < II < I < IV

(B) IV < I < II < III In order of increasing priority: Hydrogen (1.01 amu) < Flourine (18.99 amu) < Chlorine (35.45 amu) < Bromine (79.90 amu) This is also known as the *Cahl-Ingold-Prelog priority rules*

In Gas Chromatography, the Stationary Phase is a __________ while the Mobile Phase is a _____________. (A) Gas, Liquid (B) Liquid, Gas (C) Gas, Solid (D) Solid, Gas

(B) Liquid, Gas In Gas Chromatography (aka vapour-phase chromatography), the Stationary Phase is a liquid while the Mobile Phase is a gas.

Gas chromatography is often coupled with techniques such as _______________________ to provide more detail about the compound's identity. This technique in particular involves ionization and fragmenting of compounds; fragments are then run through a magnetic field which separated them by mass-to-charge ratio. The total molecular weight can thus be determined (relative conc of different fragments calculated against reference values) to identify the compound. (A) High-performance liquid chromatography (B) Mass spectrometry (C) Affinity chromatography (D) Filtration

(B) Mass spectrometry Gas chromatography is often coupled with techniques such as *mass spectrometry* to provide more detail about the compound's identity. This technique in particular involves ionization and fragmenting of compounds; fragments are then run through a magnetic field which separated them by mass-to-charge ratio. The total molecular weight can thus be determined (relative conc of different fragments calculated against reference values) to identify the compound.

Which of the following is true concerning DNA Gel Electrophoresis? (A) Negatively Charged DNA travels toward the Cathode. (B) Negatively Charged DNA travels toward the Anode. (C) Positively Charged DNA travels toward the Cathode. (D) Positively Charged DNA travels toward the Anode.

(B) Negatively Charged DNA travels toward the Anode. In Gel Electrophoresis, negatively Charged DNA (negative due to the phosphate backbone) will travel toward the positively charged anode.

Which of these principles requires that an electron in the same orbital as another electron must spin in the opposite orientation?

(B) Pauli Exclusion Principle

Which will dissolve to the greatest extent? (A) PbCl2 (Ksp = 1.60⋅10^-5) added to a solution of KCl (B) PbCl2 (Ksp = 1.60⋅10^-5) added to a solution of NaOH (C) Cu2OH (Ksp = 2.2⋅10^-20) added to a solution of KCl (D) Cu2OH (Ksp = 2.2⋅10^-20) added to a solution of NaOH

(B) PbCl2 (Ksp=1.6*10^-5) in NaOH solution. Firstly, because lower Ksp = greater solubility/dissociation; secondly, PbCl2 solubility will decrease in KCl due to the common ion effect.

Aspirin and Ibuprofen are Non-steroidal Anti-Inflammatory Drugs (NSAIDS) work by inhibiting the production of what molecules? (A) Triglycerides (B) Prostaglandins (C) Sphingolipids (D) Steroids

(B) Prostaglandins Aspirin and Ibuprofen are Non-steroidal Anti-Inflammatory Drugs (NSAIDS) work by inhibiting the production of Prostaglandins.

Which of the following is not a hydrolyzable lipid? (A) Triglycerol (B) Prostaglandins (C) Phospholipids (D) Wax

(B) Prostaglandins Non-hydrolyzable lipids include prostaglandins, steroids, corticosteroids and fat-soluble vitamins.

The final step is to determine if the sequence 1-2-3 is clockwise or counterclockwise. If it is clockwise, the designation would be __________. If it is counterclockwise, the designation would be __________. (A) D, L (B) R, S (C) S, R (D) L, D

(B) R, S The final step is to determine if the sequence 1-2-3 is clockwise or counterclockwise. If it is *clockwise*, the designation would be *R*. If it is *counterclockwise*, the designation would be *S*. L and D refer to how a chiral molecule rotates a plane of polarized light.

Hess's Law is true for variables such as enthalpy and entropy because these are _________ Variables. (A) Process (B) State (C) Fixed (D) Variable

(B) State. The law is a manifestation that enthalpy and entropy are state functions.

Dihedral/Torsional Angle is the angle between which substituents? (A) The opposing substituents on the close and distant carbon of a Newman Projection. (B) The neighboring substituents on the close and distant carbon of a Newman Projection.

(B) The neighboring substituents on the close and distant carbon of a Newman Projection.

You add sodium acetate to a solution of Acetic Acid. What will happen to the pH and why? (A) The pH will increase because an increased concentration of sodium ions will push the acid dissociation reaction backwards. (B) The pH will increase because an increased concentration of acetate ions will push the acid dissociation reaction backwards. (C) The pH will decrease because an increased concentration of sodium ions will push the acid dissociation reaction backwards. (D) The pH will decrease because an increased concentration of acetate ions will push the acid dissociation reaction backwards.

(B) The pH will increase because an increased concentration of acetate ions will push the acid dissociation reaction backwards. This is because the introduction of one of the products is shifting the equilibrium back towards reactants, according to Le Chatelier's Principle.

Geometric isomers are a subtype of diastereomers. If two substituents are on the same side of an immovable bond (double bond), they are called _______ isomers; if they are on opposite sides, considered _______ isomers. (A) trans, cis (B) cis, trans (C) optical, chiral (D) chiral, optical

(B) cis, trans Geometric isomers are a subtype of diastereomers. If two substituents are on the same side of an immovable bond (double bond), they are called *cis* isomers; if they are on opposite sides, considered *trans* isomers.

The sp2 orbitals will form _______ bonds while the p orbitals will form _______ bonds in making C2H4? (A) σ,σ (B) σ,π (C) π,σ (D) π,π

(B) σ,π The sp2 orbitals will form σ Bonds with Hydrogens' s orbitals while the p orbitals will form π Bonds with each other in making C2H4.

Calculate heat for formation for the ionization of Hydrogen Bromide: HBr(g) → H+(aq) + Br-(aq) ΔHf Br-(aq) = -120.9 kJ ΔHf HBr(g) = -36.2 kJ (A) 157.1 kJ (B) 84.7 kJ (C) -84.7 kJ (D) -157.1 kJ

(C) -84.7kJ ΔH = Σ ΔHf products - Σ ΔHf reactants heat of formation of H+ is zero ΔH = ΔHf Br-(aq) - ΔHf HBr(g) ΔH = -120.9 kJ - (-36.2 kJ) = -120.9 kJ + 36.2 kJ = -84.7 kJ

Calculate the Ksp of PbCl2 assuming that .14 grams of PbCl2 enters solution upon addition of 14.98 grams of PbCl2 to 147 mL of water? (do not use a calculator) (A) 3.54⋅10^-9 (B) 7.98⋅10^-8 (C) 1.60⋅10^-7 (D) 3.45⋅10^-6

(C) 1.60⋅10^-7 .14 grams PbCl2 ⋅ 1 mol PbCl2 / 278.1 g PbCl2 = approx. 5⋅10^-4 moles PbCl2 (actual: 5.03⋅10^-4) 5⋅10^-4 moles / .147 L = approx. 3.5⋅10^-3 M PbCl2 (actual: 3.42⋅10^-3) [Pb2+] = approx. 3.5⋅10^-3 M [Cl-] = approx. 7⋅10^-3 M Ksp = [Pb2+][Cl-]^2 Ksp = (3.5⋅10^-3)(7⋅10^-3)^2 Ksp = approx. 175⋅10^-9 (actual: 160.01⋅10^-9)

The molecule on the previous notecard has how many possible stereoisomers? (A) 1 (B) 2 (C) 4 (D) 12

(C) 4 #SI = 2^n #SI = 2^2 #SI = 4 The molecule has 2 stereocenters; thus, it has 4 different possible stereoisomers.

What is the steric number for XeF6 (periodic table: http://www.sbcs.qmul.ac.uk/iupac/AtWt/table.gif)? (A) 5 (B) 6 (C) 7 (D) 8

(C) 7 SN = σ + LP SN = 6 + 1 SN = 7

A buffer solution contains which of the following? (A) A strong acid and its conjugate base. (B) A strong acids and its conjugate acid. (C) A weak acid and its conjugate base. (D) A weak acid and its conjugate acid.

(C) A weak acid and its conjugate base. Can also be a weak base and its conjugate acid.

You add a solution of carboxylic acid mixed with amide to a seperatory funnel containing water and ether. You open the Stopcock until the entire bottom layer is in the receiving flask. At this point, you evaporate the solvent in the receiving flask, leaving you with your desired compound. What was your desired compound? (A) Water (B) Amide (C) Carboxylic Acid (D) Ether

(C) Carboxylic Acid The Carboxylic Acid was your desired compound as it is more polar than an amide and ends up in the lower aqueous phase. You evaporated the water, leaving your Carboxylic Acid in the flask. The amide is still in the receiving flask dissolved in the organic layer.

What type of reaction is used to form a Glycoside from a sugar monomer? (A) Oxidation-reduction (B) Ligase (C) Condensation (D) Hydrolysis

(C) Condensation A condensation reaction is used to form a Glycoside from a sugar monomer

Saponification could also be known as an: (A) Alcohol Hydrolysis (B) Alcohol Condensation (C) Ester Hydrolysis (D) Ester Condensation

(C) Ester Hydrolysis In a Saponification Reaction, the individual ester bonds of Triglycerol are hydrolyzed, forming individual fatty acids. It can occur in presence of an acid or a base.

You are using Size-Exchange Chromatography to separate three substances. Line these up from eluting first (left) to eluting last (right): I. Nonane II. Butane III. Hexane (A) I < II < III (B) II < I < III (C) I < III < II (D) III < I < II

(C) I < III < II Size-Exchange Chromatography to separates substances based on their molecular weight, and the smallest substances will elute last as is the case here: Nonane (C9H20)< Hexane (C6H14)< Butane (C4H10)

The pH ranges for Methyl Red, Bromthymol Blue, and Phenolphthalein are 4.4 - 6.2, 6.0 - 7.6, and 8.2 - 10, respectively. Which would best be used for titrating a weak acid with a strong base in which the steep part of the titration curve ranges from a pH of 6.2 to 11.9? I. Methyl Red II. Bromthymol Blue III. Phenolphthalein (A) I Only (B) II Only (C) III Only (D) I, II, and III

(C) III Only Methyl Red and Bromthymol Blue would change colors before the steep curve, giving you an inaccurate measurement of how much base is added to reach the equivalence point.

You double the concentration of the substance in a polarimeter tube. What happens to the observed rotation (α obs)? (A) It halves. (B) It does not change. (C) It doubles. (D) It quadruples.

(C) It doubles. OBSERVED rotation, same would happen if you doubled length.

A spot will move farther in Paper Chromatography if: (A) It is lighter. (B) It is heavier. (C) It is more attracted to the Mobile Phase. (D) It is more attracted to the Stationary Phase.

(C) It is more attracted to the Mobile Phase. This is the basis of Paper Chromatography. Our goal is to separate compounds based on their polarity, hence attraction to the mobile vs. the stationary phase.

Which bond is a result of polarization of electron clouds between non-polar molecules? (A) Dipole-dipole Interaction (B) Hydrogen Bonding (C) London Dispersion Forces (D) Covalent Bonding

(C) London Dispersion Forces Londen Dispersion Forces result from the polarization of electron clouds between non-polar molecules.

When (+) and (-) enantiomers are present in equal concentrations, they form a ________________. (A) Meso compound (B) Diastereomer (C) Racemic mixture (D) Optic chiasm

(C) Racemic mixture When (+) and (-) enantiomers are present in equal concentrations, they form a *racemic mixture*.

In Paper Chromatography, the paper acts as the ____________ Phase and the solvent in the beaker acts as the _____________ Phase. (A) Mobile, Stationary (B) Kinetic, Stagnant (C) Stationary, Mobile (D) Stagnant, Kinetic

(C) Stationary, Mobile In Paper Chromatography, the paper acts as the *Stationary Phase* and the solvent in the beaker acts as the *Mobile Phase*.

The purpose of a vacuum in a distillation is that it: (A) allows you to separate substances with extremely close boiling points more accurately. (B) allows you to separate substances with extremely distant boiling points more accurately. (C) allows you to separate substances with extremely high boiling points without damaging the substances. (D) allows you to separate substances with extremely low boiling points without damaging the substances.

(C) allows you to separate substances with extremely high boiling points without damaging the substances. The purpose of a vacuum in a distillation is that it allows you to separate substances with extremely high boiling points without damaging the substances. This is because it prevents atmospheric pressure of air from increasing and influencing BP.

Enantiomers are an example of which of the following? What are Enantiomers? (A) Constitutional Isomers (B) Conformational Isomers (C) Stereoisomers

(C). Stereoisomers Enantiomers are an example of Stereoisomers, which are defined as non-superimposible mirror images. Conformational isomers can be interconverted by only rotating bonds.

What is the pH of a .32 M solution of 143.8 mL NH3 (pKb = 4.75) when you add 45.9 mL of .13 M HCl? (A) 5.61 (B) 6.98 (C) 8.32 (D) 10.43

(D) 10.43 45.9 mL HCl ⋅ 1 L / 1000 mL ⋅ .13 moles HCl / 1 L HCl = approx. 5⋅10^-3 moles HCl (actual: 5.967⋅10^-3) 143.8 mL NH3 ⋅ 1 L / 1000 mL ⋅ .32 moles NH3 / 1 L NH3 = approx. 45⋅10^-3 (actual: 46.016⋅10^-3) 45⋅10^-3 - 5⋅10^-3 = 40⋅10^-3 moles NH3 5⋅10^-3 moles NH4+ Once again, you can use the Henderson-Hasselbach Equation here, but it will slow you down big time. Simply notice that the concentration of base will be about 10x greater than the conjugate acid, making the solution approximately 1 pH unit higher than the pKa of NH3. Also notice that the pKb was given, not pKa (pKb=14-pKa=9.25)

Which compound is being oxidized and which compound is being reduced in the following reaction?: NH3 + OCl- -> N2H4 + H2O + Cl- (A) Nitrogen is reduced; Oxygen is oxidized. (B) Chlorine is reduced; Oxygen is oxidized. (C) Hydrogen is reduced; Nitrogen is oxidized. (D) Chlorine is reduced; Nitrogen is oxidized.

(D) Chlorine is reduced; Nitrogen is oxidized. NH3 + OCl- -> N2H4 + H2O + Cl- Chlorine's oxidation state goes from +2 to -1, meaning it was reduced (gaining e's). Nitrogen's oxidation state goes from -3 to -2, which means it was oxidized (loses an electron). "Oilrig"

The breaking of a Glycosidic Linkage is what type of reaction? (A) Oxidation-reduction (B) Ligase (C) Condensation (D) Hydrolysis

(D) Hydrolysis The breaking of a Glycosidic Linkage is a hydrolysis reaction (think HydroLYSIS).

You are using Cation-Exchange Chromatography to separate three substances. Line these up from eluting first (left) to eluting last (right): I. Carboxylate II. Ammonium III. 3-Hexanone (A) III < II < I (B) III < I < II (C) I < II < III (D) I < III < II

(D) I < III < II In Cation-Exchange Chromatography, the Stationary Phase is negatively charged; thus, cations will be retained and anions will move through quickly as follows: Carboxylate < 3-Hexanone < Ammonium

(R)-Carvone and (S)-Carvone are enantiomers. They have which of the following properties in common? I. Melting Point II. Boiling Point III. Density (A) I Only (B) I and II Only (C) III Only (D) I, II, and III

(D) I, II, and III (R)-Carvone and (S)-Carvone are enantiomers and as such would have the same melting point, boiling point, and density.

The pH ranges for Methyl Red, Bromthymol Blue, and Phenolphthalein are 4.4 - 6.2, 6.0 - 7.6, and 8.2 - 10, respectively. Which would best be used for titrating a strong acid with a strong base in which the steep part of the titration curve ranges from a pH of 1.8 to 12.7? I. Methyl Red II. Bromthymol Blue III. Phenolphthalein (A) I Only (B) II Only (C) III Only (D) I, II, and III

(D) I, II, and III Because the curve is so steep, any one of these indicators would change color near the equivalence point.

Put the following bond types in order from weakest to strongest: I. Dipole-dipole Interaction II. Hydrogen Bonding III. London Dispersion Forces IV. Covalent Bonding (A) I < III < IV < II (B) I < III < II < IV (C) III < II < I < IV (D) III < I < II < IV

(D) III < I < II < IV In order from weakest to strongest: London Dispersion Forces < Dipole-dipole Interaction < Hydrogen Bonding < Covalent Bonding

You run a Gas Chromatography Column dissolving three compounds (Hexanol, Hexane, and Hexanoic Acid) in Silica Gel. Which compound is represented by the first peak in this Gas Chromatography? (A) Hexanol (B) Hexane (C) Hexanoic Acid (D) Silica Gel

(D) Silica Gel The first small peak in Gas Chromatography typically corresponds to the solvent that you dissolved your compounds in.

*Filtration* is another means to extraction to isolate a solid from a liquid by using filter paper which allows only solvent to pass through, leaving a residue and filtrate. __________________, in which a solvent's own weight pulls it through the filter, is more commonly used when the filtrate is the product of interest. _________________, in which the solvent is forced through the filter by a vacuum connected, is more common when the residue/solid is the product of interest.

*Gravity filtration*, in which a solvent's own weight pulls it through the filter, is more commonly used when the filtrate is the product of interest. *Vacuum filtration*, in which the solvent is forced through the filter by a vacuum connected, is more common when the residue/solid is the product of interest.

The octet rule is more of a "rule of thumb" to which there are many exceptions:

*Incomplete octet* - elements stable w/ fewer than 8 e's include H, He, Li, Be and B (2 ve's) *Expanded octet* - elements in the third period and greater can hold more than 8 e's in valence shell by incorporating d orbitals, e.g. Phosphorus, Sulfur, Chlorine, even Xenon *Odd # of e's* - molecule with an odd number of valence e's cannot evenly distribute them to give each atom 8; e.g. nitrous oxide (NO) has 11 ve's

When TLC is performed, compounds are generally identifited using the retention factors (or retardation factor) - describe this factor and it's equation

*Retention factor (Rf)* is relatively constant for a particular compound in a given solvent. It measures how well our product attracts to our mobile phase, given by the equation: Rf = distance compound/distance solvent (distance compound travelled / distance solvent travelled). The greater the retention factor, the higher the product has travelled up.

Describe reverse phase chromatography which is the exact opposite of typical TLC protocol.

*Reverse phase chromatography* - the stationary phase is nonpolar while the mobile phase is polar, so polar molecules elute faster and nonpolars stick.

Nucleophilic substitution reactions include SN1 and SN2 reactions, both in which a nucleophile forms a bond with a substrate carbon and a leaving group leaves. Differentiate between SN1 and SN2 reactions.

*SN1 reactions (unimolecular nucleophilic substitution rxns)* are 2 step reactions - the first step is the rate limiting step where the leaving group leaves to generate a *carbocation*. Rate of rxn depends entirely on the concentration of the substrate, as rate limiting step is carbocation formation. The more substituted the carbocation, the more stable it is (alkyl groups act as e- donors). (Rate = k[R-L] where R-L is an alkyl group with a leaving group, not something minus something.) *SN2 reactions (bimolecular nucleophilic sub- rxns)* are single-stepped in which the nucleophilic attacks and leaving group leaves simultaneously. The single rate limiting step involves two molecules. In SN2, nucleophile displaces the leaving group in a *backside attack* - for this, Nu must be strong and substrate cannot be sterically hindered - hence less substituted the carbon, more reactive it is in SN2. (Rate = k[Nu][R-L] In both cases, the substrate is often an alkyl halide, tosylate or mesylate.

α is positive, which means the substance is ____________________ and it rotated the substance to the _____________. α is negative, which means the substance is ____________________ and it rotated the substance to the _____________. Fill in the blanks using the following terms: - right - left - levorotatory (l) - dextrorotatory (d)

*α is positive*, which means the substance is *dextrorotatory (d)* and it rotated the substance to the *right*. *α is negative*, which means the substance is *levorotatory (l)* and it rotated the substance to the *left*. two enantiomers will rotate plane-polarized light in opposite directions but to the same degree of magnitude, IF their concentrations and path lengths are equal.

Calculating equivalence point.

1) We have a buffer solution of some known acid. We know our acid ionization constant. 2) Kw = Ka * Kb Kb = Kw/Ka 3) Kb = [OH-]*[conjugate acid]/[conjugate base] [OH-] = Kb*[conj base]/[conj acid] 4) pOH = -log [OH-] 5) pH = 14 - pOH

Balance the following redox reaction in acid: MnO−4(aq) + I-(aq) → Mn2+(aq) + I2(s)

10I-(aq) + 2MnO4-(aq) + 16H+(aq) → 5I2(s) + 2Mn2+(aq) + 8H2O(l)

Balance the following redox reaction in base: MnO−4(aq) + I-(aq) → Mn2+(aq) + I2(s)

10I-(aq) + 2MnO4-(aq) + 8H2O(l) → 5I2(s) + 2Mn2+(aq) + 16OH-(aq)

The next step in VSEPR is to count the number of "electron clouds" around the central atom. How many "electron clouds" are surrounding the central atom of BeCl2?

2 electron clouds.

An sp3 orbital has what percent s character and what percent p character?

25 percent s character and 75 percent p character.

VSEPR in the nutshell: Describe the electron and molecular geometry options for 2, 3, 4, 5 and 6 electron clouds.

2e- clouds: both electron and molecular geometries are linear 3e- clouds: electron geometry trigonal planar, molecular geometry can be trigonal planer (0 lone pairs), or bent/angular (1 lp) 4e- clouds: electron geometry is tetrahedral, molc geometry can be tetrahedral (0 lp), trigonal pyrimidal (1 lp), bent/angular (2 lp) 5e- clouds: electron geometry is trigonal bipyrimidal, molc geometry can be trig. bipyrimidal (0 lp), "see saw" (1 lp), "T shaped" (2 lp), or linear (3 lp) 6e- clouds: electron geometry is octahedral, molecular geometry can be octahedral (0 lp), square pyrimidal (1 lp) or square planar (2 lp)

Why is it significant that you have a "Planar" Carbocation in the middle of the reaction mechanism in terms of the kind of products you would expect to get out of this reaction?

A "Planar" Carbocation can be attacked from above or below, resulting in two isomers of the Glycoside.

The center carbon of an enantiomer is called a Chiral/Chirality Center/Stereocenter. What is that?

A Stereocenter is a tetrahedral carbon with four different substituents.

What is the difference between a disproportionation reaction and a reduction-oxidation reaction?

A disproportionation is a special type of redox reaction where the same element is simultaneously oxidized and reduced.

What is a Glycosidic Linkage?

A glycosidic linkage is the bond between two sugar monomers.

What is the difference between a Hemiacetal vs. Acetal?

A hemiacetal results from addition of an alcohol to an aldehyde (hemiketal for ketone). An acetal has a functional group with the following connectivity R2C(OR')2, and it is produced when the hydroxyl of a hemiacetal is protonated and water is lost, and the carbocation is attacked by a molecule of alcohol.

What is positron decay?

A proton decays and creates a neutron - positron decay. E.g. a C-11 atom with 6 protons and 5 neutrons ejects an electron with a positive charge (=a positron).

What is a reversible process vs. irreversible process?

A reversible process is one in which a reaction can go forwards and backwards without losing any energy, right near equilibrium in an ideal world. An irreversible process is one in which a reaction can't go forwards and backwards without losing any energy.

Why does a vacuum lower the boiling point of a substance?

A vacuum decreases the atmospheric pressure which pushes gas particles down into the liquid phase. With zero atmospheric pressure, these gas particles are more easily able to escape the liquid phase.

Explain how a weak acid and its conjugate base make for a good buffer solution?

A weak acid will react with OH-, removing it from solution. Its conjugate base will react with H+, removing it from solution. This effectively protects our solution from an increase or decrease in the pH. CH3COOH + H2O <--> H3O+ + CH3COO- Adding small amounts of NaOH, a strong base, would result in OH- ions reacting with H3O+ ions - increase in conc of acetate anion does not result in drastic pH change as would with increase in [OH-].

You add ether and water to the Seperatory Funnel. You then add a mixture of alcohol, carboxylic acid, and an alkane to the Seperatory funnel. Describe how you might isolate the carboxylic acid from the other two compounds.

Add a base to deprotonate the carboxylic acid. This way, your carboxylic acid is far more polar than the other two substances. Once you've opened the stopcock and your carboxylic acid is in the receiving flask, evaporate the water using a rotary evaporator and there you have it!

How is the common ion effect related to Le Chatelier's principle?

Addition of excess ions will alter the pH of the buffer solution. Therefore, the common ion effect takes a role in pH regulation. According to Le Chatelier's principle, addition of more ions alters the equilibrium and shifts the reaction to favor the solid or deionized form.

Write the net ionic equation for adding a solution of NaCl to a solution of AgNO3 to form the precipitate AgCl.

Ag+(aq) + Cl-(aq) -> AgCl(s)

When is agarose gel used as compared to SDS-PAGE?

Agarose gel is typically used for large compounds, like longer strands of DNA. SDS-PAGE is used for smaller compounds, like shorter strands of DNA (<50bp) and proteins.

Polyatomic cations you should know:

Ammonia cation NH4+

What is an amphoteric species? What are some examples?

An amphoteric species is one that acts like an acid in a basic environment, and like a base in an acidic environment. In Bronsted-Lowry sense - amphoteric species can gain or lose a proton, making them known as amphiprotic as well. Most common example is water. It produces OH- when reacting with a base, and H3O+ when reacting with an acid. Other examples include partialy dissociated conjugate base of a polyvalent acid (HSO4- e.g.), hydroxides of certain metals (like Zn, Al, Pb, Cr), even complex amino acids that have zwitterion intermediates. (Picture: Water reacting with an acid HA to form the conjugate acid (H3O+) and a base (A-))

Why use an oil bath as compared to a water bath when heating up the distilling flask during a distillation?

An oil bath is preferable because it will not evaporate and will also allow us to maintain a steady temperature throughout the distillation.

What is the crux of ionic bonds?

Atoms with low ionization energies will form bonds with atoms with high electron affinities (in turn, high electronegativities).

In the precipitation reaction with NaCl (aq) + AgNO3, why are Na+ and NO3- "spectator ions"?

Because they do not participate in the reaction. They are merely watching ("spectating"). AgCl has a lower Ksp value (solubility product constant - determines degree of solubility and dissociation in water) than NaNO3. Higher Ksp = dissociates more easily

Compare and contrast alkali metals and alkaline earth metals. Which have larger atomic radii?

Both alkali metals and alkaline earth metals have very low effective nuclear charges (Zeff) and low IEs, electron affinities and electronegativities, and low densities. Both exist mostly in ionic form in nature. Alkali metals have one valence electron and form univalent cations and slightly greater effective nuclear charge than alkaline earth metals, giving them slightly larger atomic radii.

What are the formulae for carbonate and hydrogen carbonate anions?

CO3^2- (carbonate) HCO3- (hydrogen carbonate)

Practice assigning Z vs E using the following practice question: http://www.chemeddl.org/collections/stereochem/priorities29.htm

Check your answer here: http://www.chemeddl.org/collections/stereochem/priorities30.htm

Practice assigning trans vs cis using the following practice question: http://www.chemeddl.org/collections/stereochem/priorities27.htm

Check your answer here: http://www.chemeddl.org/collections/stereochem/priorities28.htm

Assign R or S designation to the following compound: http://www.chemeddl.org/collections/stereochem/priorityRS2.htm

Check your answer here: http://www.chemeddl.org/collections/stereochem/priorityRS2a.htm

Assign R or S designation to the following compound: http://www.chemeddl.org/collections/stereochem/priorityRS3.htm

Check your answer here: http://www.chemeddl.org/collections/stereochem/priorityRS3a.htm

Assign R or S designation to the following compound: http://www.chemeddl.org/collections/stereochem/priorityRS4.htm

Check your answer here: http://www.chemeddl.org/collections/stereochem/priorityRS4a.htm

Complete the following practice problems to practice assigning Z and E designations: http://www.chemguide.co.uk/basicorg/questions/q-eznotation.pdf

Check your answers here: http://www.chemguide.co.uk/basicorg/questions/a-eznotation.pdf

When salt is dissolved in water, the Cl- anions become surrounded by water's Hydrogrens or Oxygens? What about the Na+ cations?

Cl- anions are surrounded by the Hydrogens and Na+ cations are surrounded by the Oxygens.

What are the formulae for perchlorate, chlorate, chlorite and hypochlorite anions?

ClO4- (perchlorate) ClO3- (chlorate) ClO2- (chlorite) HClO2- (hypochlorite)

What is the crux of complex ion formation?

Complex ions can form in aqueous solutions. A comples ion (or coordination compound) is a molecule with a cation bonded to at least one electron pair donor (which could include water). Electron pair donor molecules are called ligands - these complexes are held together by coordinate covalent bonds. Hemoglobin is a classic example of a complex ion.

Compound A (MW = 342.8) and compound B (MW = 45.82) have the same boiling points. Which will reach the detector first in Gas Chromatography? Why?

Compound B will reach the detector first because it is smaller and thus will be pushed faster by the Mobile Phase than compound A. Makes sense!

What is the main concept behind gas chromatography?

Compounds (the eluents) are gases, and they separate based on their boiling points. The column is coiled and kept inside an oven to control temperature, and the mixture is injected into the column and vaporized. Gaseous compounds travel through the column at different rates because they adhere to the absorbent in the column to different degrees. Injected compounds must be *volatile* (low MP, sublimable solids or vaporized liquids).

What type of compounds will typically flouresce using a UV lamp?

Compounds that are aromatic.

Why do compounds with lower boiling points travel further in a Gas Chromatography column?

Compounds with low boiling points will vaporize more readily and thus get dragged along by the gas Mobile Phase while compounds with higher boiling points will not vaporize as easily and will thus remain dissolved in the liquid Stationary Phase. Makes sense!

How are Constitutional Isomers similar and different from one another? How are Stereoisomers similar and different from one another?

Constitutional Isomers have the same atomic makeup (molecular formula), but a different physical arrangement. Stereoisomers have the same atomic makeup, but a different 3-D arrangement.

What is the difference between Constitutional Isomers and Conformational Isomers?

Constitutional Isomers have the same make up but a different arrangement of bonds. Conformational Isomers are a subset of diastereomers and have the same make up, the same arrangement of bonds, but their bonds are rotated differently from one another (see image).

What are the formulae for chromate and dichromate anions?

CrO4^2- (chromate) Cr2O7^2- (dichromate)

All weak bonds fall into the category of *Van der waals forces*. What are the four types?

Dipole-dipole bonds dipole-induced dipoler bonds H-bonds London dispersion bonds

When dealing with 5 electron clouds, why do nonbonding electrons tend to orient in equatorial positions rather than axial (above and below plane)?

Doing this minimizes electron pair repulsion, if they were axial there would be more 90 degree angles which is more repulsive than 120 or 180 degrees.

Prostaglandins are considered to be Eicosanoids, which are typically signaling molecules. What makes something an Eicosanoid?

Eicosanoids are molecules with 20 carbons ("eico-" means 20).

What is the difference between Electron Geometry and Molecular Geometry?

Electron Geometry is the shape of the electron clouds about the central atom. Molecular Geometry is the shape of the atoms about the central atom.

What is the Electron Geometry of BF3? Molecular Geometry?

Electron Geometry of BF3 is Trigonal Planar. Molecular Geometry of BF3 is Trigonal Planar.

What is the Electron Geometry of BeCl2? Molecular Geometry?

Electron Geometry of BeCl2 is Linear. Molecular Geometry of BeCl2 is Linear.

What is the Electron Geometry of NH3? Molecular Geometry?

Electron Geometry of NH3 is Tetrahedral. Molecular Geometry of NH3 is Trigonal Pyramidal.

What is the Electron Geometry of PCl5? Molecular Geometry?

Electron Geometry of PCl5 is Trigonal Bipyramidal. Molecular Geometry of PCl5 is Trigonal Bipyramidal.

What is the Electron Geometry of SF4? Molecular Geometry?

Electron Geometry of SF4 is Trigonal Bipyramidal. Molecular Geometry of SF4 is See-saw. There is a favoured model because nonbonding electrons take up more space and repel more. You want the fewest number of 90 degree angles.

What is the Electron Geometry of Sulfur Dioxide? Molecular Geometry?

Electron Geometry of Sulfur Dioxide is Trigonal Planar. Molecular Geometry of Sulfur Dioxide is Bent/Angular.

What is the Electron Geometry of XeF2? Molecular Geometry?

Electron Geometry of XeF2 is Trigonal Bipyramidal. Molecular Geometry of XeF2 is Linear.

What is the Electron Geometry of XeF4? Molecular Geometry?

Electron Geometry of XeF4 is Octahedral. Molecular Geometry of XeF4 is Square Planar.

Differentiate between enantiomers and diastereomers.

Enantiomers are two molecules that are nonsuperimposable mirror images of each other; diastereomers are chiral and share the same connectivity but are not mirror images, and differ at some (not all) of their multiple chiral centers.

True or False. The area under the curve of each Gas Chromatography peak is directly proportional to the speed at which the compound traveled in the column.

False. The area under the curve of each Gas Chromatography peak is directly proportional to the AMOUNT of that compound in the mixture.

How do you assign formal charges to atoms in a molecule?

Formal Charge= (# of valence electrons in free atom) - [Lone pair electrons + 1/2 shared electrons]

Flip for the base-catalyzed Saponification Reaction Mechanism.

Forms an alcohol and a soap which acts as a detergent

Name the 7 Strong Acids

HCl HBr HI HClO4 HClO3 H2SO4 HNO3

What makes High-performance Liquid Chromatography (HPLC) special compared to Normal Phase Chromatography?

HPLC works with very small quantities and has a much higher level of precision.

What is Hess's law?

Hess's law states that the total enthalpy (energy in a thermodynamic system) change for a reaction is the sum of all changes, regardless of intermediate reactionary steps or stages.

What is Hunds rule?

Hunds rule: in subshells with more than one orbital (like 2p), orbitals are filled such that there are a max number of half-filled orbitals with parallel spin. It is beneficial in avoiding electrostatic repulsion.

Why is it important to keep the sand/beads of a chromatography column wet at all times?

If it runs dry, it may cause mixing of bands, which would result in a lack of separation between your compounds of interest.

In Affinity Chromatography, what would a typical Stationary Phase be composed of? Mobile Phase?

In Affinity Chromatography, a typical Stationary Phase would be composed of an enzyme. The Mobile Phase would something the substrate is even more attracted to in order to wash it out in the end.

Is the Stationary Phase negatively-charged or positively-charged in Cation-Exchanged Chromatography? What about in Anion-Exchange Chromatography?

In CATION-Exchange Chromatography, the Stationary Phase is negatively charged; Thus, CATIONS will be retained in the column.

Describe gamma decay

In certain instances, mass is destroyed and released as energy in the form of electromagnetic radiation (E=mc^2).

At a constant pressure, the change in enthalpy is equal to what?

In such a scenario, enthalpy equals the heat (energy) added to a system. If the energy of the products is less than the reactants, it is spontaneous.

What is the difference between Intermolecular Forces and Intramolecular Forces?

Intermolecular Forces are between two difference molecules. Intramolecular Forces are between the same molecule.

What is the purpose of a DNA Ladder when doing Gel Electrophoresis?

It is a standard that allows you to determine the molecular weights of your compounds.

Glycoside Hydrolysis Mechanism.

It is the opposite of a Glycoside Formation Reaction.

What is the purpose of the Steric Number?

It tells you how many hybridized orbitals you have in the central atom. SN = σ + LP SN = Steric Number σ = # of Sigma Bonds LP = # of Lone Pairs

You add CH3COO- to water. What do you predict will be the resulting pH? Why?

It will be greater than 7 because CH3COO- is the conjugate BASE of a weak acid (CH3COOH, acetic acid). Remember, the conjugate base of a weak acid is strong. Adding CH3COO- to H2O results in increase in hydroxide ions. CH3COO- + H2O --> CH3COOH + OH-

Draw the generic structure of a Sphingolipid.

Made of a high MW amino alcohol sphingosine, the X is where phosphate group would be

In TLC, the stationary phase is often a silica gel which is polar and hydrophilic. The mobile phase on the other hand is usually a nonpolar organic solvent. Based on this, what type of compounds would move more quickly through the stationary phase, and what molecules would stick to the gel more?

Nonpolar molecules move farther and more quickly through the gel. Polar molecules stick more to the gel. This is normal-phase; there is also reverse phase discussed later.

How do enantiomers rotate plane-polarized light?

One enantiomer will rotate plane-polarized light to the same magnitude but in opposite direction of its mirror image (if conc and path lengths are equal). A compound that rotates the light in the right direction (clockwise) is dextrorotatory and labelled (+). A compound that rotates light left (counterclockwise) is levorotatory and is labelled (-).

The Carbons of C2H2 only need 2 hybrid orbitals each, and they have 2 orbitals with lone pairs of electrons. What will they do?

One of the 2s orbital electrons jumps up to one of the 2p orbitals. One of the three 2p orbitals then hybridize with the single 2s orbital, forming two sp orbitals and two p orbitals with a lone electron in each. In a triple bond, one sp orbital and two p orbitals participate, with the p orbitals forming the pi bond. This is known as *sp hybridization*

If Carbon only has two lone pairs of electrons, how does it form four bonds to make Methane (CH4)?

One of the 2s orbital electrons jumps up to one of the 2p orbitals. The three 2p orbitals then hybridize with the single 2s orbital, forming four sp3 orbitals with a lone electron in each. This promotion of one 2s electron to the 2p-z orbital produces four valence electrons. All these four orbitals point towards vertices of a tetrahedron to minimize repulsion - explains tetrahedral shape of methane. This is known as *sp3 hybridization*, where the three p and one s orbitals merge to form new, hybridized shapes.

The Carbons of C2H4 only need 3 hybrid orbitals each, yet they have 2 orbitals with lone pairs of electrons. What will they do?

One of the 2s orbital electrons jumps up to one of the 2p orbitals. Two of the three 2p orbitals then hybridize with the single 2s orbital, forming three sp2 orbitals and one p orbital with a lone electron in each. This is known as *sp2 hybridization*, and it is the unhybridized p orbital that participates in the pi bond of a double bond.

What are the formulae for phosphate, hydrogen phosphate and dihydrogen phosphate anions?

PO4^3- (phosphate) HPO4^2- (hydrogen phosphate) H2PO4- (dihydrogen phosphate)

What is the difference between unpolarized light and plane-polarized light?

Plane-polarized light has all of its waves are oriented in the same direction while unpolarized light has waves oriented in all directions.

Enantiomers have identical physical and chemical properties, so how can one separate a racemic mixture into its two constituent isomers?

Reacting two enantiomers with a single enantiomer of another compound will lead to two diastereomers - say two enantiomers that have only one chiral carbon, they will be labelled (+) and (-). If each is reacted with a (+) enantiomer of another compound, then two diastereomers will be formed labelled (+,+) and (-,+) - since they differ a two chiral centers, they are diastereomers. Diastereomers have different chemical and physical properties and can be separated using common lab techniques (crystallization, filtration, distillation, etc.) The diastereomers can then be reacted to regenerate the original enantiomers.

How are SN2 reactions stereospecific?

SN2 reactions are *stereospecific* because they perform backside attack due to steric hinderance and stability (simultaneous reaction!) and so are accompanied with an inversion of relative configuration

What are the formulae for sulfate, sulfite and hydrogen sulfate anions?

SO4^2- (sulfate) SO3^2- (sulfite) HSO4- (hydrogen sulfate)

What is the purpose of chromatography?

Separate substances based on their various properties such as size or polarity. In all forms, the concept is the same - the more similar a compound is to surroundings (polarity, charge, etc), the more it will stick to and move slowly through its surrounding.

Is Silica Gel polar or non-polar?

Silica Gel is polar.

The first step in drawing dot strcutures is to determine the number of valence electrons for each atom involved. How many valence electrons does Silicon have?

Silicon has 4 valence electrons.

Describe the special role that Sphingolipids play within the Nervous System.

Sphingolipids are a key component of myelin which composes the Myelin Sheath.

Draw a Staggered vs. Eclipsed Newman Projection

Staggered is much more stable than eclipsed conformation.

Differentiate between a strong acid-strong base titration and a weak acid-strong base titration

Strong-acid strong-base titration sees very little influence on adding base to the pH - small amounts of addition will not change [OH-] significantly and pH remains relatively constant. It will only alter concentrations of H+ and OH- near the equivalence point and elicit most substantial pH changes there. The equivalence point for strong acid-strong base (monovalent species) is pH=7. The first diff with a weak acid-strong base titration is that the initial pH of the weak acid solution is greater than the initial pH of strong acid, as weak acids do not dissociate completely. The pH changes gradually with addition of base and does not have as sudden a rise as strong acid strong base titrations. The equivalence point is above pH=7

What is the purpose of a Redox Titration vs. an Acid/Base Titration?

THEY HAVE THE SAME PURPOSE! The purpose is to find the concentration of a solution. The difference between these methods is not their purpose but their methodology. One uses the equivalence point between an acid and its base while the other uses the equivalence point between an oxidized species and its reduced species.

Monosacchs contain both a hydroxyl group (good nucleophile) and carbonyl group (good electrophile) - thus they undergo intramolecular interactions to form cyclic *hemiacetals* from aldoses and *hemiketals* from ketoses. What happens?

The OH group attacks the carbonyl carbon to form a closed ring. The only stable ring structures due to ring strain are 6C (*pyranose*) and 5C (*furanose*) rings. When this happens, the carbonyl carbon becomes chiral and is referred to as an *anomeric carbon* - the two different ring formations are referred to as *anomers*

What about the structure of Phospholipids makes them work so well for Lipid Bilayers?

The Phosphate group is polar, which will face away from the bilayer and the Fatty Acid tails are non-polar and will thus face toward the center of bilayer towards each other.

Why is it that the smaller compounds elute last in Size-Exchange Chromatography?

The Stationary Phase used in Size-Exchange Chromatography consists of beads with small holes that run through them. The smaller compounds will have to make their way through these small holes while the big compounds will go around the beads, quickly making their way through the column.

What is the purpose of the condenser in a distillation?

The condenser will cause the compound with the lowest boiling point (lower than the temperature the mixture has been heated to) to condense and collect as liquid in the receiving flask.

Why can't you use a strong acid and its conjugate base for a buffer solution?

The conjugate base of a strong acid is EXTREMELY weak and as such would not react with H+, leaving your solution vulnerable to decreases in pH.

How does a fractionating column help you more accurately separate compounds with very close boiling points?

The fractionating column contains steel wool, beads, or another substance to which the gases can condense on. This way, the gases will have to condense and evaporate multiple times further away from the heat source in order to escape the distilling flask and make it to the condenser. This way, only the compound with the lower boiling point will be able to escape.

A scientist is determining the Observed Rotation (α) of a substance. How will the scientist use the analyzer apparatus to determine this?

The scientist will rotate the analyzer until she observes light coming through the analyzer. At this point, the scientist would measure the degree to which the scientist rotated the analyzer.

The sp orbitals will form what type of bonds while the p orbitals will form what type of bonds in making C2H2?

The sp2 orbitals will form σ Bonds with Hydrogens' s orbitals while the p orbitals will form π Bonds with each other?

At the equivalence point, what is true concerning the concentration of the reduced vs. oxidized species?

Their concentrations are equal. This is always true about equivalence points. Whenever you hear "equivalance point" you should immediately think: "equal concentrations."

What about the structure of waxes makes them so good at repelling water?

Their two hydrophobic tails are what repel water.

Name the four fat-soluble Vitamins and describe the basic function of each.

These fat-soluble vitamins generally serve as cofactors. E.g. vitamin K in blood coagulation for liver-produced tissue factors

What is the difference between paper chromatography and Thin Layer Chromatography (TLC)?

They are the same thing, except that in TLC, the stationary phase is always Silica Gel.

How does Ksp relate to other equilibrium constants?

They are very similar. The key difference is that, because the solvent is a liquid, it does not need to be considered in the calculations.

In Normal Phase Chromatography, what is the typical Stationary Phase that is used? (A) Wool beads (B) Organic solvent (C) Silica gel (D) Paper

They typical Stationary Phase in Normal Phase Chromatography is Silica Gel, which is polar. Normal Phase Chromatography features a polar stationary phase and nonpolar mobile phase.

Why is this reaction called Saponification? Why do Fatty Acids make for good soap molecules?

This reaction is called Saponification because it results in the formation of soap molecules. Fatty Acids make for good soap molecules because they have a non-polar tail that will trap non-polar greasy particles. Then the polar heads will be attracted to water, causing the grease to get dissolved in and washed away by the water. Surfactant in the alveoli is an example.

What is a titration?

Titrations are performed by adding small volumes of a solution of known concentration (titrant) to a known volume of an unknown concentration, until completion of the reaction is achieved at the equivalence point.

What is the purpose of *VSEPR (Valence Shell Electron Pair Repulsion)* Theory?

To help represent and predict the shape of a molecule.

What is the purpose of an extraction?

To separate compounds based on their polarity.

True or false: entropy (disorder) always increases?

True. In an isolated system, there is always a net increase in entropy - entropy change from initial state is at maximum.

True or False? Sodium Acetate increasing the pH in a solution of Acetic Acid is an example of the Common Ion Effect.

True. Sodium Acetate increasing the pH in a solution of Acetic Acid is an example of the Common Ion Effect.

True or False? σ Bonds can freely rotate while π Bonds cannot.

True. σ Bonds can freely rotate while π Bonds cannot.

True or false: configurational isomers have two types, enantiomers and diastereomers, both of which can be considered *optical isomers*

True: configurational isomers have two types, enantiomers and diastereomers, both of which can be considered *optical isomers* (because the different spatial arrangement of groups in these molecules affects rotation of plane-polarized light)

True or false: two enantiomers will rotate plane-polarized light in opposite directions but to the same degree of magnitude, IF their concentrations and path lengths are equal.

True: two enantiomers will rotate plane-polarized light in opposite directions but to the same degree of magnitude, IF their concentrations and path lengths are equal. Note the equation incorporates concentration (c) and path length (l)

Draw the energy diagram for the following compound: https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Newman_projection_butane_-sc.svg/120px-Newman_projection_butane_-sc.svg.png

Understand which compounds have highest vs lowest energy, and thereby stability.

In a Fischer Projection, vertical bonds represent dashed or solid lines? Horizontal bonds represent dashed or solid lines?

Vertical bonds represent dashed lines (meaning the bond goes into the page). Horizontal bonds represent solid lines (meaning the bond goes out of the page).

What is the half-equivalence point?

When concerning polyvalent acids and bases, the half equivalence point is when half of a given species has been protonated (or deprotonated). CH3COOH + NH3 --> CH3COO- + NH4+ [CH3COOH] = [CH3COO-]

Why is Xenon able to form bonds even though it is a noble gas?

Xenon is past the 3rd period of the periodic table and so has enough valence shells to be able to expand it in order to form bonds.

2Cu+ -> Cu(s) + Cu2+ Is this a disproportionation reaction? Why/why not?

Yes. As we can see, copper is being both oxidized and reduced in this reaction. Recall a disproportionation rxn is a special type of redox reaction where the same element is simultaneously oxidized and reduced.

What procedure can be used to separate enantiomers from each other?

You do Affinity Chromatography (Column or Gas) in which the Stationary Phase contains a chiral enzyme that only binds to one of the two enantiomers.

2 electrons are paired and produce own magnetic fields in opposite directions. What sort of magnetism is this, and how would they interact with an external magnetic field?

electrons are said to be diamagnetic; they will be weakly repelled by an external magnetic field

What is the pH at the equivalence point of a strong acid-strong base titration curve?

pH = 7

Determine the pH of a buffer solution that is 0.24M NH3 and 0.20M NH4Cl.

pH = 9.33

What is the Henderson-Hasselbach equation?

pH = pKa + log[A-]/[HA]

sp orbitals have what percent s character and what percent p character?

sp orbitals have 50 percent s character and 50 percent p character.

sp2 orbitals have what percent s character and what percent p character?

sp2 orbitals have 33 percent s character and 67 percent p character.

What do the different quantum numbers tell you about the electron? 1) principal quantum number (n) 2) angular momentum/azimuthal quantum number (l) 3) magnetic quantum number (ml) 4) spin quantum number (ms)

1) the principal quantum number (denoted by n) tells you what main energy level/shell the electron is in - larger integer = higher energy shell 2) the azimuthal quantum number (denoted by l) tells you about the shape of the orbital the electron is in - values of l depend on n, and can range from 0 to (n-1). For n=1, the only possible number for l is 0 (s orbirtal); when n=2, l can be 0 or 1 (p orbital); n=3, l can be 0, 1 or 2 (d orbital) 3) the magnetic quantum number (denoted by ml) tells us about the orientation of an orbital around a nucleus - the values depend on l; ml = any integral value ranging from -l to +l. If l=0, ml can equal only 0 (indicates sphere for an s orbital); if l=1, ml can equal -1, 0 and +1 (indicates dumbbell shape for p orbital, 3 possible orientations are x-, y- and z- axes) 4) the spin quantum number (denoted by ms) tells you about the spin of the electron - value can be wither +1/2 or -1/2; 2 e's in the same orbital must have opposite spin, and are said to be paired. electrons in different orbitals with the same ms value are said to have parallel spin

The N/Z ratio represents the neutron:proton ratio. Why is Carbon 12 stable compared to Carbon 14?

C12 has a N/Z ratio of 1 (6/6) whereas C14 has a ratio of 8/6 - Carbon 14 undergoes spontaneous decay due to attain a more stable ratio.

What is electronegativity? Describe its patterns on a periodic table.

Electronegativity is a measure of the attractive force an atom exerts on an electron in a chemical bond. Greater electronegativity = more it attracts electrons. Electronegativity increases along a period (left to right) - alkali metals are the least electronegative, while halogens are the most (Fluorine being the most electronegative atom). It however decreases down a group - this is due to increasing valence shells. The Pauling electronegativity scale ranges from 0.7 (cesium) to 4.0 (fluorine). A general rule is that a difference in electronegativity between atoms in a bond of >1.7 means its ionic (e.g. NaCl 2.1)

True or false: The Bronsted Lowry acid-base definitions are the most inclusive.

False: The most inclusive are Lewis acid and base definitions. Every Arrhenius acid is a BL-acid, and every BL-acid is a Lewis acid. The reverse is not necessarily true though - Lewis acids include species such as BF3 (boron trifluoride) and AlCl3 (aluminum chloride) that can accept electron pairs but lack hydrogens to donate.

The stable N/Z ratio increases to ~1.5 as you increase the number of protons (>20) - why?

For larger nuclei with greater number of protons, more neutrons are needed due to increases in electrostatic force (repulsive). When Z increases beyond 83, electrostatic forces are so repulsive and strong that any such element undergoes radioactive decay (nuclear strong force can only act on very very short distances, remember).

Effective nuclear charge increases: (A) along a period (B) down a group (C) up a group I. A only II. A and B III. B and C IV. A and C

I - A only Effective nuclear charge (Zeff) is the electrostatic interaction between a nucleus and valence electrons - measure of net positive charge on outermost electrons. It increases along a period due to increasing number of protons but constant number of valence shells, pulling them closer due to stronger electrostatic pull. Down a group, the number of valence shells increases while the number of protons and valence electrons remains constant - thus Zeff stays constant, but the electrons are less tightly bound to the nucleus due to greater size.

Ka and Kb are the acid dissociation constant and basic dissociation constant, respectively. How do you distinguish a strong acid/base from a weak one with Ka/Kb?

If Ka < 1.0 / Kb <1.0, then it is a weak acid or base. Acids and bases that only partially dissociate in aqueous solutions are called weak acids and bases.

What is the relationship between Ionization energy and atomic size?

Inversely proportional. The higher the IE, the smaller the size, and the less likely the atom is to give up an electron. If you look at Coulomb's Law, you can see that a force (which can be IE) is inversely proportional to the radius: F = k(q1q2)/r^2 - charges can be the same but if r increases, F decreases. That's why Lithium has a lower IE than hydrogen.

What is ionization energy? Why does ionization energy increase as you go up a group and along a period?

Ionization energy (IE) is the energy required to remove an electron from a gaseous species - it is an endothermic process and requires input of heat energy. IE is proportional to effective nuclear charge (Zeff) - the greater an atoms Zeff, the closer valence electrons are to the nucleus, and thus the more difficult it to remove the tighter bound electrons. Thus, ionization increases as you go up a group (bottom to top) and along a period (left to right) because of decreasing size.

Which has a greater electron affinity? Lithium or Berylium? Why?

Lithium. This breaks the normal electron affinity trend because Berylium's new electron will be added to a far away p orbital, which will experience more shielding than Lithium completing its s orbital.

What is the equation for solving the binding energy?

Mc^2 + BE = (Z)mpc^2 + (A-Z)mnc^2 + (Z)mec^2 where... M = mass of the atom as a whole BE = binding energy (Z)=atomic mass (# of protons = # electrons) (A-Z) = # of neutrons mp, mn, me = mass of protons, neutrons, electrons, respectively

Which of the following likely has a higher second ionization energy, sodium or magnesium?

Na - sodium has a higher second ionization energy than magnesium because it only has one valence electron, whereas Mg has 2. The first ionization energy is the energy needed to remove the first electron to form a univalent cation; the second is that needed to remove the second e- forming a divalent cation. Active metals have low ionization energies (thus low electronegativities). Values for 2nd IE are disproportionally larger for group 1 metals, but not so for group 2 monovalent cations (Mg+, Ca+ e.g.), because after the first IE, group 1 cations achieve noble-gas like configuration.

Write out the electron configuration for Carbon. Is it dia- or paramagnetic?

Paramagnetic. Electrons in orbitals fill up according to Hund's rule - i.e. they will up such that every orbital in a subshell is singly occupied before any one is doubly occupied.

The half life of a substance is the time it takes for a sample to decrease by half its amount. What does this tell you about the rate of decay?

The rate of decay exponentially decreases over time, with the most significant decay being the first half life.

Why don't protons in a nucleus repel each other?

There is a nuclear strong force present at extremely close distances in nuclei - strong enough to overcome electrostatic repulsive forces. This is why energy input (=binding energy) is required to separate a nucleus.

Kw = [H3O+][OH-] = 10^-14 What is this ionization reaction, and why is there no reactant in the equilibrium equation?

This rxn is the autoionization of water: H2O(l) + H2O(l) <--> H3O+(aq) + OH-(aq) One water molecule donates a H to another to produce the hydronium ion and the hydroxide ion. The water autoionization (dissociation) constant, Kw, has been determined to be 10^-14 at room temp experimentally. The equation has no reactant in the denominator because remember, water is a pure liquid and its concentration does not change, thus it remains out of the equation. Therefore, we know the concentrations of both products is 10^-7. Unless the temperature of the water is changed, Kw cannot change.

What are characteristics of transition metals?

Transition metals are quite malleable, have low EAs, IEs and electronegativities; high MPs and BPs, high densities. They are good conductors of electricity, and have loosely held electrons that progressively fill d orbitals.

Why is water left out of equilibrium equations?

Water is a pure liquid and it's concentration does not change in acid or base dissociation reactions.

Atomic radius ______ across a period and ______ down a group

decreases; increases

Calculate the pH of a 1.0M solution of CH3COOH

pH = 2.38. Acetic acid, CH3COOH, is a weak acid, and therefore will not dissociate completely. Thus, we must use (x) as a value or change and make assumptions to get an approx but accurate value for pH. CH3COOH + H2O <---> H3O+ + CH3COO- Initial: 100 - 0 0 Change: -x +x +x Initial conc is before any dissociation - use of (x) as a value for change - losing x amount of acetic acid would inevitably cause gain in the same amount for the products, based on the balanced equation of the reaction. From there, you form an equilibrium equation: Ka = [H3O+][CH3COO-]/[CH3COOH] = 1.8*10^-5 = (x)*(x)/(1.00-x) Ka's given value is 1.8*10^-5. At this point, we make an assumption that x << 1.00, which means that a loss would result in an insignificant difference on overall pH. Thus, 1.00-x = ~1.00 1.8*10^-5 = (x^2)/1.00; x = 0.0042M = [H3O+] pH = -log[H3O+] = -log 0.0042 = 2.38

What is pKa? pKb?

pKa is a measure of acid strength. In contrast, pH is a measure of [H+] in a solution. The smaller the pKa, the smaller the pH, and the stronger the acid (more easily proton is lost). pKa = -logKa pKb is the analog for pKa in relation to bases. pKb = -logKb

When electrons are in parallel spin and the magnetic fields add together, the situation is said to be ___________

paramagnetic - one or more unpaired electrons; pulled into an external magnetic field