3rd week of September chemistry review
The acid ionization constant is also known as the: (A) Acid association constant (B) Acid dissociation constant (C) Acid solubility constant (D) Acid precipitation constant
Acid Dissociation constant
A researcher adds equal amounts of acetic acid and sodium acetate by moles. Will the resulting solution be acidic or basic? (pKa of acetic acid is 4.75)
Acidic, bc the pKa of acetic acid is less than the pKb of acetate pKb of acetate is 14-4.75 = 9.25. 4.75 is less than 9.25 so solution is more acidic.
What is the Azimuthal Quantum number(l) for the orbital from which an electron is lost to form Na+1? 3 2 1 0
0... its losing it from the s orbital
What is alpha decay?
A natural process that spits out an alpha particle, a 4/2 He.
What is beta decay?
A neutron in the atom becomes a proton and an electron with high energy. The electron is a beta particle and is ejected from the nucleus. A new atom is formed, with one proton more and one neutron less than the original.
A radioactive sample is giving off gamma rays. What is occurring on the atomic scale?
A nucleus in an excited state releases a photon, going to its ground state. in gamma decay, the nucleus is in an unstable high energy state. It releases this extra energy by emitting a photon, going to the more stable ground state. No nucleons come or go, so the element remains the same
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 the solution. Its conjugate base will react with H+, removing it from the solution. This effectively protects our solution from an increase or decrease in the pH.
Phosphorous has two known isotopes that weigh 30 amu (90%) and 31 amu (10%). What is the most likely atomic mass of a single phosphorus atom? A: 30 B: 31 C: 30.9 D: 30.1
A:30 It is asking for the mass of a SINGLE atom. it is not asking for the atomic weight. Which would be 30.1
What are following PKas? Phenol sulfonic acid (RSO3H) Phosphoric acid (RPO3H)
Phenol 11 sulfonic acid (RSO3H) --> -3 Phosphoric acid (RPO3H) --> 2-3
What are following PKas? R-NH3+ ROH2+
R-NH3+. --> 9 ROH2+. --> -1.74
What is the equipment called that we use in extractions? What comes out first?
Separatory funnel. The more dense liquid. The aqueous phase usually is the one to come out first.
Compare 3 types of distillation
Simple distillation: under 150 and are 25 apart Vacuum distillation: BP is over 150. We lower the pressure to reduce the BP to prevent degrading the subtance Fractional distillation: is when BP's are closer than 25 apart
How is IR spec plotted?
as percent transmittance, amount of light that passes through the sample and reaches the detector vs. wavenumber
when do reversible processes occur?
at equilibrium conditions
How do you calculate effective nuclear charge for an atom? What would the value be for Fluorine?
atomic number - inner shell electrons. F would be 9 - 2 = 7
The indicator used was a stronger base than one of the analytes that is being tested. If the researcher still tries to use this indicator, how could this affect the experiment? in terms of when it will react in relation to the equivalence point
The indicator will react before the equivalence point is reached
How does TS affect delta G?
it doesn't. Delta G is a state function and depends only on the initial and final states
what does butanoic anhydride look like? and how is it formed>
it has 4 carbons on BOTH sides of the central oxygen formed by rxn of two molecules of butanoic acid
match lewis acid and lewis base with nucleophile and electrophile
lewis acid = electrophile lewis base = nucleophile
What is the filtrate?
liquid that has passed through a filter, we want the product to be here
what 4 factors determine nucleophilic strength?
more negative charge, less electronegative (less likely to share e density), not bulky molecules, aprotic solvents
what does it mean if the solvent system is polar?
most polar compound will travel the furthest up the card, resulting in the largest Rf. example of reverse-phase chromatography. stationary phase would be non-polar
For an IR spec. what are there some situations where we cannot record an absorbtion?
must result in a change in the bond dipole moment. we can't get an absorption from O2 or Br2 but we can from HCl or CO. Symmetric bonds such as the triple bond in C2H2 will also be silent
Would adding a salt affect buffering capacity?
no
Are ethers polar or non polar?
non polar
Which of the following is a Bronsted-Lowry acid, but not a Lewis acid? none of the above I2 H2O HF
none of the above All Bronsted-Lowry acids ARE Lewis acids. Bc donating the hydrogen means accepting the electron pair that used to make up the covalent bond with Hydrogen
Which has a bigger ionic radius... nonmetals close to the metalloid line or non metals further away?
nonmetals close to the metalloid line
What is nucleophilic acyl substitution
nucleophilic acyl substitution has a LG that leaves. The carbonyl group also gets reformed after (as long as there is a LG)
what is 0th law of thermodynamics?
objects are only in thermal eq. when Temperatures are equal
DELETE specific rotation equation
observed rotation/ (concentration of solution x length of tube)
What is superheating?
occurs when a liquid is heated to a temp. above its BP without vaporization. Due to gas bubbles not being able to overcome atmospheric pressure and surface tension
What is gamma decay?
occurs when an electron and positron collide, emitting a high energy gamma ray
What is high performance liquid chromatography? (HPLC)
similar to CC but uses sophisticated computer-mediated solvent and temperature gradients. Used if the sample size is small or if forces such as capillary action will affect results.
What is the normal pH of blood?
slightly basic (7.35-7.45)
What is the analyte in a titration?
solution of unknown concentration
Describe process of decarboxylation
some may spontaneously decarboxylate when heated. RXN proceeds through a six-membered ring in its TS. The product then tautomerizes from the enol to the more stable keto form
What are following PKas? sp3 carbon sp2 carbon sp carbon
sp3 carbon 50 sp2 carbon 45 sp carbon 25
difference between specific heat and heat capicty
specific heat is energy required to raise temperature of one gram of substance by 1 degree celcius. heat capcity is the product of mc (mass times specific heat)
What is reverse phase chromatography?
stationary phase is nonpolar so polar molecules will move up very quickly.
differentiate structural (constitutional) isomers and stereoisomers
structural mean they have same molecular formula. Stereoisomer means they have same connectivity, but arranged differently in 3D
what is trend between number of hydroxyl groups and BP?
the more OH groups, the higher the boiling point
How does TS affect rxn rate?
the more energy it takes to create the TS, the slower the rxn will go
what is the eluent?
the solvent that is used for the mobile phase
What is chromatography?
uses physical and chemical properties to separate and idenitfy compounds from a complex mixture
whats something to know about gabriel synthesis and the strecker synthesis?
Both methods result in a racemic mixture of amino acids of L-acids and D-acids
A saturated solution of copper (II) carbonate (Ksp = 1.4 x 10^-10) is added to an equal volume of a saturated solution of cobalt (II) carbonate (Ksp = 1.4x10^-13). What will occur? (what will precipitate)
Cobalt (II) carbone will precipitate bc the Ksp will be greater than Ksp for cobalt (II) carbone, which leads to it precipitation
compare extraction, filtration, and recrystallization
Extraction: We have a mixture of compounds. We put them both in a mixture of 2 solvents, one that dissolves each one. We then seperate them in a funnell and evaporate the solvents at the end and are left with just the product. Filtration: Isolates a solid residue from a liquid (filtrate) Recrystallization: the product is dissolved in a minimum amount of hot solvent. If the impurities are more soluble, the crystals will reform while the flask cools, excluding the impurities
The alpha hydrogen of a carboxylic acid is: I. more acidic than the hydroxyl H II: less acidic than the hydroxyl H III. relatively acidic, as organic compounds go
II and III pKa is 12 vs 16. The hydroxyl H is more acidic
How do the titration curves of a strong acid and strong base compare to a weak acid and a strong base? Consider buffering capacity, the shapes of the curves, and the equivalence points.
For strong acid, notice the little change in pH until right before the equivalence point, then a sharp increase.For the weak acid, notice the gradual change in pH as base is added, showing buffering capacity. The middle of that buffering capacity is where pH=pKa. Near its equivalence point, it will also sharply increase.The equivalence points are halfway between the pH before and after the steep increase.
What is flash column chromatography?
Forcing the solvent through the column using gas pressure
Which of the following are Lewis bases? I. Ag+ II. H2O III. NH3
II and III only NH3 and H2O are lewis bases bc nitorgen and oxygen can donate lone pairs. Ag+ is a lewis acid bc it can accept a lone pair into an unoccupied orbital
What happens if you react a secondary alcohol with PCC?
It will become a ketone
Which of the following metals is not a stong base as a salt with OH-? Rb Ca Mg
Mg all the alkali metals are strong bases when they form salts with OH- Only the heavier alkaline earth metals are strong bases when they form salts with OH-. Mg and Be are not
A researcher quickly mixes together a buffering solution with equal concentrations of sodium bicarbonate (pKa = 6.4) and sodium carbonate in pure water and proceeds with their reaction. What is the pH of this solution? 7.1 5.3 6.4 6
6.4 Use the HH equation. If sodium bicarbonate and sodium carbonate are in equal amounts, then [A-] / [HA] will be equal to one. so the pH will equal the pKa
What is the pH of a solution that contains [OH-] of 9.84x10^-8 M. 8.21 6.84 6.99 7.05
6.99 Think through this logically!! Remember the math that we do is merely an estimation. Especially if two numbers are really close, you got to think about it logically
A researcher prepares a 0.030 M Ba(OH)2 solution for use in a titration. He is trying to get a more accurate concentration measurement of a solution that is approximately 0.2 M HCl. If the researcher is titrating 20 mL of the HCl solution, approximately what amount of Ba(OH)2 solution should he expect to use? 100 mL 133 mL 50 mL 67 mL
67 mL remember Ba(OH)2 is a dibasic species. So the OH concentratoin is 0.06. Use MV = MV to get answer.
A student improperly mixes sodium bicarbonate (pKa = 6.4) and sodium carbonate by adding too much sodium carbonate. The professor asks him to measure the pH of the unreacted buffer solution. Which pH is most likely? 7.1 9 6.1 4
9 Use HH equation. Buffers are most effective when the pH of the solution is within 1 of the pKa of the acid. Outside that range, it cannot properly buffer. We are told that the student added too much conjugate base. So the pH must be at least 1 unit more basic, or greater, than the acid's pKa of 6.4. Which makes 9 the best answer
What is the pH of a buffer solution that contains 3.3x10^-5M NH3 and 7.2x10^-5M NH4+ (Ka = 5.6x10^-10) 8.3 7.6 10.7 9.0
9.0 NH4 and its conjugate base are less than a factor of 10 apart so pH should be about the same as pKa. There is a tiny bit more acid than base so maybe a tiny bit less than what we predict.
If 0.03 mol of HCl is added to 0.5L of a buffer solution that is 0.24 M NH3 and 0.2M NH4Cl (pKa 9.25) what is the resulting pH? 9.1 1.2 10.2 7.1
9.1 Since we know that this is a buffer solution, we know it resists changes in pH. Since the concentrations of weak acid and conjugate base are approximately equal before adding HCl, we can guess the starting pH is close to the pKa of 9.25. So it should be within one unit. We can do the math: there is .06 M of Hcl so NH3 will be .24 - .06 = .18. and we add .06 to NH4+. so we see that there is a little more acid so it should be just under 9.25
A researcher add 0.25 mol of sodium acetate to 1 L of water. What will be the resulting pH? (Acetate has a Kb of 5.6x10^-10) 4.9 9.1 1.5 12.5
9.1 write out equilbirum expression. [OH-] and [CH3COOH' will be the same. and acetate will be 0.25 M. So the pOH is about 5 and the pH is about 9.
What is the fingerprint region on an IR spec?
1500 - 400 range. very complex vibration patterns. We never use these.
What does divalent mean?
2 valence electrons
Methyl red is an indicator that changes color between pH 4.4 and 6.2. This could be used to indicate the equivalence point in a titration of an acid with which of the following pKa's? 8.4 2.8 5.3
2.8 the pH at which the indicator changes color needs to be at least one pH unit greater than the pKa of the compound being tested to ensure all of the weak acid has reacted before the indicator changes color. 2.8 is the best answer
What is the height of each peack proportional to in NMR?
# of H's
What is the Kb of Cl- if the pKa of HCl is -7? (A) 1 ⋅ 10^-21 (B) 1 ⋅ 10^-14 (C) 1 ⋅ 10^-7 (D) 1 ⋅ 10^7
(A) 1 ⋅ 10^-21 pKw = pKa + pKb 14 = -7 + pKb 21 = pKb pKb = -log(Kb) 21 = -log(Kb) Kb = 1 ⋅ 10^-21
In the hydrolysis of salts, a cation and anion will be freed and may interact with water. Which of the following anions would be a stronger base than water? (A) CN- (B) Br- (C) CH3CO2- (D) NO3-
(A) CN-The conjugate base to a strong acid will not react with water; the weaker that the acid is, the stronger its conjugate base is.Both CH3CO2- and CN- are conjugate bases to weak acids (acetic acid and hydrogen cyanide, respectively). In this case, we must compare the acids' pKa's to water's pKa: acetic acid has a pKa of 4.75, whereas hydrogen cyanide has a pKa of 9.2.Water has a pKa of 7, so only CN- is a stronger base than water.
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 base with a strong acid in which the steep part of the titration curve ranges from a pH of 7.4 to 3.5?I. Methyl redII. Bromthymol blueIII. Phenolphthalein (A) I Only (B) II Only (C) III Only (D) I, II, and III
(A) I Only Bromthymol blue and phenolphthalein would change colors before you reach the steep part of the curve.
Which of the following is the conversion factor from Joules to electron-Volts (eV)? (and what do the other numbers mean?) (A) 1 eV = 6.626 ⋅ 10^-34 J (B) 1 eV = 1.6 ⋅ 10^-19 J (C) 1 eV = 3 ⋅ 10^8 J (D) 1 eV = 9.11 ⋅ 10^-31 J
(B) 1 eV = 1.6 ⋅ 10^-19 J (A) [6.626 ⋅ 10^-34]is equal to Planck's constant (C) [3 ⋅ 10^8] is equal to the speed of light (D) [9.11 ⋅ 10^-31] is equal to the mass of an electron
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.
When 1.0 mole of ZnO(s) decomposes, the ΔH = 348 kJ/mol of heat energy. This tells you that the formation of ZnO(s) is: (A) Endothermic (B) Exothermic (C) In equilibrium (D) Endergonic
(B) Exothermic The FORMATION of ZnO(s) is exothermic because it is the reverse reaction of the decomposing.
An electron's total energy is composed of what two types of energy?(A) Thermal and kinetic energy (B) Kinetic and electric energy (C) Electric and potential energy (D) Thermal and electric energy
(B) Kinetic and electric energy
In the hydrolysis of salts, a cation and anion will be freed and may interact with water. Which of the following cations would be a stronger acid than water? (A) Na+ (B) NH4+ (C) Mg2+ (D) K+
(B) NH4+Group 1 cations and larger group 2 cations do not react with water. Ammonium, on the other hand, will react with water and donate a proton.
Which of these principles requires that an electron in the same orbital as another electron must spin in the opposite orientation? (A) Aufbau principle (B) Pauli exclusion principle (C) Hund's rule (D) Electron configuration principle
(B) Pauli exclusion principle`
You have a buffer solution containing a weak acid (pKa = 4.2) that has a pH of 7. A base is added, increasing the OH- concentration of the buffer solution by 10x the original amount. What is the new pH? (A) -3 (B) 6 (C) 8 (D) 17
(C) 8 Because we are told that the hydroxyl concentration of the solution has increased tenfold, we do not need to worry about the buffering capabilities.You can use the Henderson-Hasselbach equation to solve this type of problem, but you should be able to solve it conceptually just knowing that the pH scale is a logarithmic one.
What is the pH of a buffer solution that contains 3.3 ⋅ 10^-5 M NH3 and 7.2 ⋅ 10^-5 M NH4+ (Ka = 5.6 ⋅ 10^-10)? (A) 7.56 (B) 8.32 (C) 9.02 (D) 10.67
(C) 9.02 Don't even waste your time pulling out the Henderson-Hasselbach equation for this one! The concentrations of the conjugate acid and base are less than a factor of ten apart and there is more acid than base, so the pH must be slightly less than the pKa (9.25). Most buffer solution questions on the MCAT should be solved intuitively without using the HH equation!
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. Or a weak base and its conjugate acid
When Dmitri Mendeleev published the first periodic table, it was based on the periodic law. Which of the following best describes the periodic law? (A) Elements' physical properties depend on their atomic numbers in a periodic way. (B) Elements' chemical properties depend on their atomic numbers in a periodic way. (C) Elements' chemical and physical properties depend on their atomic numbers in a periodic way. (D) Elements' chemical, physical, and nuclear properties depend on their atomic numbers in a periodic way.
(C) Elements' chemical and physical properties depend on their atomic numbers in a periodic way.
Which of the following statements about electrolytes are correct?I. Strong electrolytes are solutes that will dissociate completely in a solvent and will dissolve.II. Weak electrolytes may remain ion-paired to some extent.III. Non-electrolytes are covalent compounds that do not dissociate into ions. (A) II only (B) I and III only (C) II and III only (D) I, II and III
(C) II and III onlyStrong electrolytes will dissociate completely, but do not necessarily have to be soluble. All ionic compounds are strong electrolytes.Weak electrolytes may remain ion-paired to some extent and nonelectrolytes are covalent compounds that do not dissociate into ions.
The laws of thermodynamics dictate transformations of energy from one form to another. Which law of thermodynamics states that closed systems will always favor an increase in entropy? (A) Zeroth law of thermodynamics (B) First law of thermodynamics (C) Second law of thermodynamics (D) Third law of thermodynamics
(C) Second law of thermodynamicsThe second law of thermodynamics states that systems will always favor an increase in entropy.
What is the pH of a 143.8 mL solution of .32 M 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 (NH3) will be about 10x greater than the conjugate acid (NH4+), making the solution approximately 1 pH unit higher than the pKa of NH3.Also notice that the pKb was given, not pKa (pKb = pKw - pKa = 14 - 4.75 = 9.25)
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 redII. Bromthymol blueIII. Phenolphthalein (A) I Only (B) II Only (C) III Only (D) I, II, and III
(D) I, II, and IIIBecause the curve is so steep, any one of these indicators would change color near the equivalence point.
Tosylate
*contain functional group -SO3C6H4CH3 -Used to protonate a hydroxyl group to make it a better LG for nucleophilic substitution rxn -serves as PG
what is another oxidation state of Fe other than 2+ and 3+?
+6 giving it the same electron configuration as calcium. It would lose all of its d electrons in this instance
What are some propertires of phosphoric acid?
- 3 acidic hydrogens - excellent buffer (3 H's span nearly the whole ph scale) - release a lot of energy when cleaved
What can you do and not do with maniuplating fischer projections?
- rotating it 180 degrees, switching 2 pairs, switching 3 atoms while holding one constant wont have any affect -these will have an effect! rotating 90 degrees, switching 2 atoms,
What are the required conditions for two solvents to be used together in an extraction? Which goes in which layer?
- two solvents must be immiscible (dont mix) - aqueous phase will have more polar solvent, organic phase will have the nonpolar solvent
what are two thigns we can do after extraction to obtain the product?
- use a rotary evaporator to evaporating the solvent - we can do a wash. This is when a small amount of solute is used to extract and remove impurities, rather than the compound of interest
In a hemiacetal, the central carbon is bonded to what 4 things?
-OH, -OR, -H, and -R
In a hemiketal, the central carbon is bonded to what 4 things?
-OH, -OR, -R, -R
what is the suffix when an aldehyde is part of a ring?
-carbaldehyde
Memorize Molecular Geometry Chart
...
Carbonic acid is a diprotic acid with pKa values of 6.4 and 10.3. A researcher prepares a solution with a pH of 11.5 using sodium bicarbonate and sodium hydroxide. What is the ratio of bicarbonate to its conjugate base? 7.9x10^-6 1.3x10^5 16 0.06
0.06 bicarbonate is still a weak acid itself. So when sodium hydroxide is added, it will react with the bicarbonate. Use HH equation. pH is 11.5. We will use 10.3 as the pKa bc we are using bicarbonate instead of carbonic acid. For the math part, raise 10 to the power of both sides to remove the log. It asks for HA:A so put 1/10 at the end
How much 1 M HCl would need to be added to a solution to have the same effect as adding 0.300 L of a 2.5N acid?
0.75 L ... Think through these logically first than try and do the math. Then check your work again with logic
Which of the following groups contains exactly one nonmetal? 1 5 2 9
1 (Hydrogen)
measurements for pressure
1 atm = 760 mmHg = 760 torr = 101.325 kPa
what are the 4 peaks we need to know from IR spec?
1) O-H has a broad peak at 3300 (alcohols) or 3000(carboxylic acids) 2) C=O (carbonyl) has a sharp deep peak at 1700 3) N-H bonds have a sharp peak at 3300
What are the 6 main shifts in Proton NMR?
1) alkyl groups: 0-3ppm 2) alkynes: 2-3ppm 3) alkenes: 4.6-6ppm 4) aromatics: 6-8.5ppm 5) aldehydes: 9-10ppm 6) carboxylic acids 10.5-12ppm
Predict what will happen 1) If Z > 82 2) If N/Z is too high 3) If N/Z is too low
1) alpha decay 2) Beta decay 3) Positron emmission or electron capture
A mixture of sand, benzoic acid, and naphthalene in ether is best separated by... (3 steps)
1) filtration (will get the sand out) 2) basic extraction (benzoate anion is formed and becomes dissolved in the aqueous layer, while naphthalene remains in the ether) 3) evaporation will yield purified naphthalene
what favors the kinetic product? (4 things) (rate, reversibilitiy, temp, base)
1) rxn that are rapid 2) irreversible 3) at low temp 4) with a strong sterically hindered base
what favors the thermodynamic product? (4 things) (rate, reversibilitiy, temp, base)
1) rxn that is reversible 2) high temp 3) slow 4) with weak and small bases
Common soluble compounds
1) salts containing NH4+ 2) group 1 cations 3) NO3- and CH3COO- anions.
compare 3 types of ring strain... 1) angle strain 2) torsional strain 3) nonbonded strain
1) when bond angles deviate from their ideal values by being stretched or compressed 2) eclipsed, gauch interactions 3) result when nonadjacent atoms or groups compete for the same space. includes flagpole interactions such as tert butyl group will want to be equatorial and not axial
If a coefficient is not mentioned in an chemical equation, what is it assumed to be?
1. NOT 0. It is 1
Rank the following in reactivity towards nucleophiles: ester, amides, carboxylic acids, and anhydrides (2 are tied) and why
1. anhydrides 2. esters and carboxylic acids 3. amides -anhydrides have 3 EWG. Esters have 2 EWG. Amides have an electron-donating group.
What is the pKa of CN-
10
What is the ideal ratio for weak acids to conjugate bases in a buffer?
1:1 This is because buffering capacity is measured by the amount of strong base or strong acid that must be added to change the solution's pH by
Which of the following is the correct relationship between various Bohr radii? A: 1:3:5 B: 1:1:1 C: 1:2:4 D: 1:4:9
1:4:9 (n^2)
what is Naphthalenemethanol?
2 aromatic rings with an COH group sticking out of one of the rings
How do you figure out the number of possible stereoisomers?
2^n (n = number of chiral centers)
within how many bonds does splitting occur in NMR? Why do atoms split?
3. Each H can be in a alpha or beta state. We have to look at all the possibilities and this is what gives us doublets and triplets and so forth.
Which of the following subshells do electrons enter first? 4s 3d 2d 4p
4s REMEMBER 2d does not exsist
What is the pKa of CH3COO-
5
A researcher has an HCl solution with a pH of 0 and a solution of 1 M NaOH. She wants to create a 100ml solution with a pH of 2. What volumes of HCl an NaOH must be added to accomplish this? 39.5 mL HCl, 60.5 ml NaOH 10.0 mL HCl, 49.7 ml NaOH 50.3 mL HCl, 49,7 mL NaOH 57.4 mL HCl, 43.6 mL NaOH
50.3 mL HCl, 49,7 mL NaOH determine H+ concentrations of pH of 0 and 2. We get 1M and .1M. So 99% of the H+ needs to react with NaOH in order to have .1M left. So the HCl concentration needs to be 1% larger than the NaOH concentration
What is abbreviation for mass number?
A
Treating 2-methyl-1-propanol with methysulfonyl chloride in base, followed by reaction with pyridinium chlorochromate and a final step in strong acid, will give an end product of a: 2-methyl-1-propanol b: 2-methylpropanol c: 2-methylpropanoic acid d: 2-methyl-1-propane
A the methysulfonyl chloride is a PG so nothing gets reacted and it is later removed by the strong acid
Titrations become much more interesting once your consider polyvalent acids or bases, in which a single molecule can act as either an acid or a base multiple times. What will its titration curve look like, and what does that represent?
A curve with varying slopes, with flatter slopes representing the buffering capacity of one of the multiple acid or base groups
In order to separate a biological effector from a solution, which chromatographic technique would be the most effective?
Affinity
A fossil is known to be 7,400 years old. If the fossil started with 30g of carbon-14, how much nitrogen-14 is present? (half life of 5,730 years) A: 12 B: 7 C: 23 D:18
After carbon-14 goes through a half life, half of it will become Nitrogen-14. This means that after 5,730 years, there will be 15g of Carbon left, and 15g of Nitrogen.
WHat is group one and group two called on periodic table?
Alkali metal (1) and alkaline earth (2)
What are following PKas? Allylic/Benzylic alpha carbon of ketone carboxylic acid carboxylic acid with F3
Allylic/Benzylic 45 alpha carbon of ketone 20 carboxylic acid 4 carboxylic acid with F3 0
What product is formed when 238U undergoes alpha decay, and what is its charge?
Alpha decay only affects the nucleus so no electrons are lost. the new atom will always have a -2 charge
The Q value for a rxn is less than K. if the rxn is not allowed to proceed, then as the temperature is increased, K decreases while Q stays the same. At a certain temperature, Q and K are the same. What does this tell us about the delta G and delta S values for this rxn at the starting temp?
At starting temp. Q<K. low Q means more reactants. So the rxn needs to proceed forward so Q can equal K. So the rxn is spontaneous at this lower starting temp. once Q and K become the same as temp increases, this means the rxn will no longer move forward. If temp keeps going up, Q>K and rxn will be non spontaneous. If the rxn is non-spontaneous only at high temp, then delta S is negative
What is one metal that is really unreactive?
Au, it does not corrode easily which makes it better for jewelry
Which of the following types of electrons are typically used to create long-lasting bonds between multiple atoms, and why? A: 1s electrons, since they have the weakest interactions with the nucleus B: Valence electrons, since they have the weakest interactions with the nucleus C: 1s electrons, since they are held closest to the nucleus D: Valence electrons, since they are held closest to the nucleus
B
What is Bohr's model of an atom? A: a nucleus with shells where elctrons are most likely to be found B: electrons orbiting a nucleus with quantized angular momentum C: Electrons in a soup of + charge D: Electrons orbiting a nucleus like palents
B Bohor observed that light is only absorbed at certain wavelengths. In order for this to be true, the electrons needed to have angular momentum exactly equal to the energy of the photon of light. This means that electrons must have quantized angular momentum.
A carbon atom participates in one double bond. As such this carbon contains orbitals with: A: hybridization between the s-orbitak and one p-orbital B: hybridization between the s-orbital and two p-orbitals
B Its sp2
the hydrogens of phosphoric acid have pKa values that: A. allow high buffering capacity over a small pH range B: allow moderate buffering capacity over a large pH range C: allow low buffering capacity over a small pH range D: do not allow buffering
B it covers the whole pH range bc it has 3 hydrogens with pKa values
The catalytic production of dihydroxyacetone and glyceraldehyde 3-phosphate (2-hydroxy-3-oxopropyl dihydrogen phosphate) from fructose-1,6-bisphosphate ({[(2S,3S,4S,5R)-3,4-dihydroxy-5-[(phosphonooxy)methyl]oxolan-2-yl]methoxy}phosphonic acid) is what type of reaction? A. Aldol condensation B. Retro-aldol reaction C. Dehydration D. Nucleophilic attack
B nomenclature is not needed. we are making a ketone and an aldehyde from a single molecule.
Which of the following carboxylic acids will be the most acidic? Which is 2bd most acidic? A: CH3CHClCH2COOH B: CH3CH2CCl2COOH C: CH3CH3CHClCOOH D: CH3CH2CH2COOH
B and then C The more EWG there are, the more acidic it is bc it will stabilize the carboxylate anion. It also become more acidic when the distance between the EWG and the acid functionality. This would make C more acidic than A.
Which statement is true about mass spec. and why are the other ones false? A: It is used to determine the properties of an element B: It separates ions based on their mass to charge ratio C: The ions are accelerated only through electric field D: The mass spectrometer os bombarded with neutrons
B) It separates ions based on their mass to charge ratio It does not determine properties of an element. It is bombarded with ELECTRONS in order to ionize the components of a sample and the ions are subjected to both electric and magnetic fields in the spectrometer
Name the 8 metalloids
B, boron Si, silicon Ge,germanium, As, arsenic, Sb, antimony Te,tellurium Po, polonium At, astatine
Which of the following would have the least polar bond? Cl-P Na-Cl F-N B-H
B-H F and Cl will pretty much create polar bonds with anything
MnO4- reacts with I- to form I2 and Mn2+ in a basic solution. What is the balanced equation for this reaction? A: 2MnO4- + 10I- + 16H+ --> 5I2 + 2Mn2+ + 8H2O B: 2MnO4- + 10I- + 8H20 --> 5I2 + 2Mn2+ + 16OH-
B... It says it reacted in basic solution so H+ should not be apart of the reaction. pay attention to details!!
Why does the second ionization increase by a much larger factor for Na than for Mg? A: Zeff decreases for the second ionization of Mg, but not for Na B: Zeff increases for second ionization of Na, but not for Mg
B: Zeff increases bc it is now a cation
When you add a solution of NaCl to a solution of AgNO3, why is it that the precipitate is AgCl but not NaNO3 in terms of Ksp?
Because AgCl has a lower Ksp value, meaning it is more likely to form a precipitate at a lower concentration.
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.
Why doesn't Hydrogen produce a continuous spectrum of light?
Because its orbitals have specific energy differences between them, resulting in light waves with specific energy levels and thus specific wavelengths. It cannot produce every different wavelength level.
Carbon-14 has a half-life of 5,730 years and forms nitrogen-14 when it decays. which type of decay is this?
Beta decay bc a neutron becomes a proton
Blood uses a carbonic acid (pKa = 6.4) and bicarbonate buffer system, maintaining a pH of approximately 7.4. If HCl is added to the buffer system, what result does this have on the solution?
Bicarbonate reacts with H+, and the pH decreases slightly.
A student has heard that carbon-14 is an unstable isotope, and will decay to form nitrogen-14, but is unsure how the atom's net charge changes during this beta decay. How does the carbon-14 atom's charge change in this process, if at all? A: the formerly neutral carbon-14 becomes an anion B: the formerly cationic carbon-14 becomes neutral C: the formerly neutral carbon-14 becomes a cation D: the neutral carbon-14 remains neutral
C It is neutral before it decays, even though it is unstable. In beta decay, a neutron becomes a proton as the neutron emits an electron. Because the negative electron is lost, the atom gains a +1 charge, becoming cationic.
Which of the following best describes the final product of an aldol condensation? A: 1,3-dicarbonyl B: 1,2-dicarbonyl C: alpha, beta-unsaturated carbonyl
C in the second step of aldol condenation, the aldol is dehydrated forming a double bond. the doulbe bond is between the alpha and beta carbons.
2 common trends in the absobtion chart
C-C < C=C < C=-C (triple bond has higher absorption than one bond) Bond between any atom and H is always high
What is Henry's Law?
C=kP (C= concentration of dissolved gas, P= partial pressure of the gas, k= the constant) [A]1/P1 = [A]2/P2 = kh [A] can also be replaced with S1 and S2
what are two common buffers?
CH3COOH and CH3COO-NA+ / NH3 and NH4+Cl-
Which of the following would be formed if methyl bromide were reacted with phthalimide and followed by hydrolysis with an aqueous base?
CH3NH2 the rxn will result in teh formation of methyl phthalimide. and the hydrolysis then yeields methylamine
What are following PKas? CH4 NH3 H2O
CH4 = 50 NH3 = 35 H2O = 15.7
Which has a greater electron affinity: Nitrogen or Carbon? Why?
Carbon. This breaks the normal electron affinity trend because Nitrogen's new electron will be added to a p orbital with another electron, which increases the amount of repulsion that the new electron will experience.
what is formula for carbonic acid, bicarbonate, and sodium bicarbonate?
Carbonic acid: H2CO3 Bicarbonate: HCO3- Sodium bicarbonate: NaHCO3
Rank the following in order of decreasing oxidation state: amine, carboxylic acid, aldehyde, alkane
Carboxylic acid > Aldehyde > amine > alkane carboxylic acid has 3 C-O bonds, aldehyde has 2 C-O bonds. That is what is meant by oxidation state
what are 4 acyl derivatives that the MCAT will focus on? what do they all replace? How are they formed?
Carboxylic acids, amides, esters, anhydrides. The last 3 all replace an -OH group with another LG. All formed by a condensation reaction with a carboxylic acid.
what do lewis acids and lewis bases form when they interact?
Coordinate covalent bonds
Chromate ion dicrhomate ion oxolate ion Peroxide ion thocyanate ion thiosulfate ion
CrO4 2- Cr2O7 2- C2O4 2- O2 2- SCN - S2O3 2-
Which conversion between carboxylic acid derivatives is NOT possible by a nucleophilic rxn? A. Carboxylic acid to ester B. Ester to carboxylic acid C. Anhydride to amine D. Ester to anhydride
D In order from highest to lowest, this hierarchy is anhydrides > carboxylic acids and esters > amides. This means that derivatives of higher reactivity can form derivatives of lower reactivity but not vice versa. Nucleophilic attack of an ester cannot result in the corresponding anhydride bc anhydrides are more reactive than esters.
In the presence of an acid catalyst, the major product of butanoic acid and 1-pentanol is: A: 1-butoxy-1-pentanol B: butyl pentanoate C: 1-pentoxy-1-butanol D: pentyl butanoate
D the rxn describes if esterification, in which the nucleophilic oxygen atom of 1-pentanol attacks the electrophilic carbonyl carbon of butanoic acid, ultimately displacing water to form pentyl butanoate. The acid catalyst is regenerated from 1-pentanol's released proton
The laws of thermodynamics dictate transformations of energy from one form to another. Which law of thermodynamics states that the entropy of a system approaches some constant value as its temperature approaches absolute zero? (A) Zeroth law of thermodynamics (B) First law of thermodynamics (C) Second law of thermodynamics (D) Third law of thermodynamics
D) 3rd law
The actual mass of Helium is .03 amu less than its predicted mass (the mass expected based on the individual masses of its protons, neutrons and electrons). In the case of Helium, .03 amu is considered the: (A) Binding energy (B) Atomic mass (C) Atomic mass difference (D) Mass defect
D) Mass defect. The mass defect is the mass difference between the actual and predicted mass of an atom.
How does energy of electron relate to principal quantum number?
E = -R(h)/n^2 ... E and N are directly proportional
what equation do we use to solve emf when it deviates from standard conditions?
E = E^o - (0.0592/n) * log Q ... where n is the number of moles of electrons
How do you relate wavelength and frequency?
E=hf
What equation for energy equates a change in mass to a change in energy?
E=mc^2
Lyman, Balmer, Paschen series are all groups of emission lines based on this model. How do these three series differ?
Each series specifies the wavelengths emitted when an electron drops from higher energy levels to the first, second, and third energy level respectively.
Noble Gases have a value of zero for which trend?
Electron affinity
A researcher is looking to renovate his basement, and is worried about radioactive isotopes. Upon further review, he finds a large quantity of Carbon-11, which is decaying into Boron-11. Which of the following types of decay is this sample most likely undergoing?
Electron capture... not positron emission. Still not exactly sure why
What is the equation for magnetic force in terms of magnetic field strength and velocity of an ion?
F = qvB F = Magnetic Force q = Charge of ion V = Velocity of ion B = Magnetic Field Strength
True or false? A buffer has its maximum buffering capacity when its pH is greater than its pKa.
False. A buffer has its maximum buffering capacity when its pH is EQUAL to its pKa.
True or false? If a reaction is spontaneous (thermodynamically favorable), then it must occur rapidly.
False. A reaction's kinetics and its thermodynamics are not necessarily related! Thermodynamics only predict if a reaction will be spontaneous, not its rate.
True or false? Metalloids can also be called semimetals, because they can alternatively act as metals or nonmetals in the same environment.
False. Metalloids (also called semimetals) can act as either metals or nonmetals DEPENDING on the environment. For example, Boron will act like a nonmetal when surrounded by Sodium but like a metal when surrounded by Fluorine.
True or false? Due to their metallic properties, metalloids are considered conductors just as metals are.
False. Metalloids are considered semi-conductors
Which equation can be used in tandem with F = qvB in order to calculate the mass of an ion in a mass spectrometer based on the radius of the circle?
Fc = m(v^2/r)
compare what effects rate of rxn in SN1 and SN2 rxns
For SN1 it is only affected by the concentration of the substrate (w/LG). For SN2 it is affected by the substrate (w/LG) and the nucleophile.
How are amides formed?
From an amine and a carboxyl group or its acyl derivatives
Which of the following amino acids does not have an L-enantiomet? A. Cysteine B. Threonine C. Glutamic acid D. Glycine
Glycine All amino acids are chiral and have both L and D enantiomers. Glyceine is differnet bc it is achiracl bc its R group is H.
What makes an element travel further within the detector? (Mass spec)
Greater mass will curve more slowly than smaller masses so it will make it travel further
Which groups are rarely found as free elements in nature and why?
Groups 1&2 bc they are highly reactive due to their ability to easily lose valence electrons. They always occur in a combined form with another element. If in doubt, go with a group 1 metal
A researcher prepares a solution with an OH- concentration of 10^-8 by adding a weak electrolyte. Which of the following did the researcher likely add to the solution? HCl NaOH NH3 H2CO3
H2CO3 weak acids/bases are good ex. of weak electrolytes. We know from the OH concentration that this is indeed an acid solution. So we will choose the weak acid
at physiological pH, which two forms of phosphoric acid have the highest concentrations?
H2PO4- and HPO4(2-)
For a polyvalent or polyprotic acid or base, the same molecule can act as an acid or base multiple times. Using the example of H2SO4, explain the concept of gram equivalent weight.
H2SO4 is a diprotic acid, so half of a mole of H2SO4 can donate as many H+ as a mole of a normal acid (like HCl). The gram equivalent weight is how much of the polyprotic acid is needed to act like a 1N acid, and in this example, is equal to half of the molecular weight of H2SO4.
A student has learned that polar compounds will often dissolve or interact with pure water. Which of the following polar compounds will produce an acidic solutoin when added to pure water? Na2SO4 KCl HBr MgI2
HBr We want to find a cation that is more acidic than the anion is basic in order to make an acidic solution. Mg, K, and Na will all not react with water.
What are following PKas? HCl HF HI HBr
HCl -6 HF 3 HBr -8 HI -9
Which of the following would fully ionize at the lowest temperature? He Rb Br Mg
He. The 2nd and 3rd ionizations will keep getting harder and harder. The element with the least electrons will take the least energy to fully ionize, which corresponds to the lowest temperature.
What is the difference between heat, temperature, and enthalpy?
Heat is the transfer of energy due to change in temperature.Temperature is the measure of the average kinetic energy of molecules.Enthalpy is referred to as the heat transfer from the perspective of the system during reactions.
Nucleophilic acyl substitution is favored by: I. basic solution II. acidic solution III. LG that are strong bases
I and II Nucleophilic acyl substitutions are favored in basic solution, which makes the nucleophile more nucleophilic; in acidic solution, which makes the electrophile more electrophilic; and by good LG. However, strong bases do not make good LG; weak bases do
Consider (E)-2-butene and (Z)-2-butene. This is a pair of what type of isomers? I. Cis-trans isomers II. Diastereomers III. Enantiomers
I and II Remember, Cis-trans isomers are a subtype of diastereomers in which the position of substituents differs about an immovable bond.
Which of the following are common names for carboxylic acid derivatives? I. Acetic anhydride II. Formic acid III. Methyl formate (what is this)
I and III Formic acid is a carboxy acid, not a derivative Methyl formate is an ester with a methyl group attached to the oxygen. there will also be a H attached to the main carbon hence the For-.
When succinaldehyde is treated with lithium diisopropylamide (LDA), it: I. becomes more nucleophilic II. becomes less nucleophilic III. generates a carbanion
I and III only When any aldehyde or ketone with alpha hydrogens is treated with a strong base like LDA, it forms the more nucleophilic enolate carbanion
Which of the following will convert cyclohexanol to cyclohexanone? I. Chromium trioxide II. Pyridinium chlorochromate III. sodium dichromate
I, II, and III PCC can also turn 2 prime OH to a ketone
Why is a single bond stronger than a pi bond? I. pi bonds have greater orbital overlap II. s-orbitals have more oberlap than p-orbitals III. sp3 hybridization is always unstable
II only Bond strength is determined by the degree of orbital overlap; the greater the overlap, the greater the bond strength. Sp3 is also very stable
A resonance structure describes: I. The hybrid of all possible structures that contribute to electron distribution II. a potential arrangement of electrons in a molecule III. the single form that the molecule most often takes
II only pay attention to the wording each resonance strcuture is not neccessarily the most common Statement I is just reversed
Which of the following will convert CH3CH2CH2OH to CH3CH2CHO? I. CrO3 II. PCC III. K2Cr2O7
II only. Its an alcohol to an aldehyde
How do resonance and EWG affect the acidity of a molecule?
IT makes it more acidic because they stabilize the negative charge on the oxygen after the hydrogen leaves
Describe what would happen if the indicator was a stronger acid or base than the titrand being used.`
If the indicator is a stronger acid or base than the titrand being used, then the first titrant that is added will react with the indicator instead of the titrand! This means you wasted a solution
When would you have to use distillation instead of extraction?
If the product itself is a liquid that is soluble in the solvent.
When will a pH indicator change color?
In a specific pH range for that indicator.
compare electron capture and positron emmission
In positron emission, a proton is converted to a neutron by emitting a positron. In electron capture, an outside electron is pulled inside the nucleus and combined with a proton to make a neutron.
An experimenter studying the photoelectric effect on a magnesium plate wants to increase the number of electrons ejected from the metal surface in a given amount of time. Which of the following changes should he make to achieve his goal?
Increase the number of photons. Not increasing the frequency
Does adding H+ to a solution of CaF2 result greater or less solubility of CaF2? Why?
Increased solubility because F- reacts with the H+, causing the solubility reaction to move forward according to Le Chatelier's principle (removing products).
Does adding NH3 to a solution of AgCl result greater or less solubility of AgCl? Why?
Increased solubility because NH3 reacts with the Ag to form a complex ion, causing the solubility reaction to move forward according to Le Chatelier's principle.
What is the indicator in titrations?
Is a weak acid or base that will change colors when the pH of the solution is within 1 unit of its pKa, the range in which the compound changes between its protonated and deprotonated states.
what is an acyl compound?
It always has a carbonyl, an R chain of carbons, and then another group (Cl, NH2 etc.)
Why does IUPAC not consider Zn(s) a transition metal?
It has a complete d-subshell, even in its +2 cation form.
Why is the isotope 12-C not useful for NMR?
It has no magnetic moment it needs to have an odd mass number or an even mass number with an odd aotmic number. 2-H and 10-B would both be useful
What happens to the radius of the electrons orbital when it becomes excited?
It increases the radius
Key oxidation number rule for Oxygen
It is +2 in OF2 and it is -1 in BaO2
What is there to know about Ultraviolet Spectrosopy?
It is most useful for studying compounds containing double bonds or heteroatoms with lone pairs that create conjugated systems. The more conjugated the compound, the lower the energy of the transition and the greater the wavelength of maximum absorbance
What does it mean in terms of energy levels of electrons to say that the ionization energy of an atom is -13.6 eV?
It would require 13.6 eV to move an electron from n=1 to n=infinity, making the Hydrogen atom an ion.
How would you make a "super buffer" while keeping a 1:1 ratio?
Just keep adding equal amounts of acid and base to the solution
What is the equation for the energy of a photon in terms of the energy of the emitted electron?
KEp = KEe + WF KEp = Kinetic energy of the photon KEe = Kinetic energy of the electron WF = Work function
Knowing that Ka = [H3O+][A-]/[HA], write out the formula for the base dissociation constant Kb.
Kb = [B+][OH-]/[BOH]
1 mol of a weak acid (HA) is added to 1L of water. What is the equilibrium expression for Kb?
Kb = [OH-][HA] / [A-]
keto vs enol
Keto has a double bond to the oxygen and enol has an alcohol and a C==C double bond
which is thermodynamically favored between keto and enol forms?
Keto is thermodynamically favored
in relation to acidity of alpha hydrogens, which are more acidic between aldehydes and ketones?
Ketones are less acidic due to the elctron donating propertires of the additional alkyl group
What is the relationship between Ka and Kw?`
Kw (the autoionization constant of water) is the Ka (acid dissociation constant) for water.
How does angular momentum relate to principal quantum number?
L = (n*h)/2pi ... L and N are directly proportional
What reagent should you use to reduce a carboxylic acid to a primary alcohol?
LiALH4... (NaBH4 is not strong enough)
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.
How to determine if titrant was a strong acid/base?
Look at the end of the graph, a strong acid will be super low and a strong base will be super high
Phosphoric acid is a triprotic acid with pKa values of 2.1, 7.2, and 12.4. If equal amounts of disodium phosphate and monosodium phosphate are dissolved in solution, what will be the approximate pH of the resulting buffer solution? 5 7 12 2
Monosodium phosphate is NaH2PO4. Disodium phosphate is NA2HPO4. So these have 2 and 1 protons respectively. We will use HH equation here and will use the pKa going from 2 protons to 1 proton. Equal amounts are used to pH will be approximately equal to pKa.
what is rule for determining number of peaks?
N + 1. If it has 3 adjacent carbons it will have 4 peaks.
which out of NH2 and NO2 is an EWG?
NH2 is electron donating and NO2 is EWG. NO2 will make it more acidic
are spontaneous rxns irreversible?
NO they are always reversible
compare nuclear strong force with electrostatic force
NSF is the force between nucleons that holds a nucleus together. It opposes and overcomes the electrostatic force between protons, which causes their repulsion.
Formula for sodium carbonate
Na2CO3
In the hydrolysis of salts, a cation and anion are freed and can interact with water. Which of the following salts will produce a basic solution when added to pure water? HBr KCl NaClO NaHSO4
NaClO the best answer will have a non reactive cation and an anion that will react with water. Na is group 1 so it will not react. ClO- is the conjugate base to a weak acid making it able to react with water
Which solution will work better as a conductor? Deionized water or pure diethyl?
Neither bc they both lack electrolytes. Polarity has nothing to do with it being a conductor!
How will protium behave in an electric field as compared with deuterium? which will accelerate faster?
Neither protium nor deuterium will accelerate. Since they are both neutral, neither will experience force due to an electric field.
A student wants to make a permanent magnet, and is learning about paramagnetic and diamagnetic materials. Which material would make a better magnet?
Neither. They do not generate magnetic fields by themselves. They both interact with external magnetic fields however.
Are catalysts involved in the net ionic equation?
No
What will occur if additional solid PbCl2 is added to a saturated solution of PbCl2?
No additional PbCl2 will dissolve or precipitate
could you use a nonpolar solvent with a nucelophile?
No because nucleophiles are polar. and like dissolves like. We want our nucleophile to dissolve
Are hydroxyl groups good LGs?
No they are not. They need to be protonated first
Do spectator ions affect the rate of the rxn?
No, otherwise it would be a catalyst
are carbonate and phosphate salts soluble?
No, unless they are bound to a group 1 or ammonium salt
Are the lanthanide and actinide series considered transistion metals?
No.
Are spectator ions even involved in the rxn?
Not usually
Berylium-7 undergoes radioactive decay to form lithium-7. What type of decay is this?
Positron emission bc a proton becomes a neutron
Which is more soluble in water... CO2 or SO2?
SO2 bc it has a bent shape and is polar. CO2 is linear
What is the retardation factor? Rf
Rf = distance spot moved / distacne solvent front moved. So it would be the distance the colored dot when up divided by high high the wet solvent went up the paper (bc it will always pass the colored dot) - compounds with higher affinity for the stationary phase have smaller retardation factors and take longer to pass through
Henrys law equation
S1/P1 = S2/P2
The solubility constant at 20C is 1.5 x 10^-3 mol L^-1 atm^-1. What is the gas solubilitiy at a pressure of 500 torr? Which equation would you use to solve this?
S=kP S will be gas solubility. k is the constant. p is the partial pressure
What is an efficient way to identify an unknown compound and determine its properties?
Spectroscopy
What is a key difference between thin-layer chromatography and column chromatography?
TLC uses capillary action to move the solvent up the plate. CC uses gravity to move the solvent and compounds down the column.
What accounts for the actual mass of Helium being .03 amu less than its predicted mass (the mass expected based on the individual masses of its protons, neutrons and electrons)?
The .03 amu is a result of the mass being converted into energy as the protons, neutrons, and electrons are brought together to form the atom
Compare the Aufbau principle, the Pauli exclusion principle, and Hund's rule.
The 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 bus seat" rule, which states that electrons will fill in orbitals one at a time before pairing up.
Before absorbing an ultraviolet photon, electrons can be found in: A: the HOMO only B: the LUMO only
The HOMO only only after absorbing ultraviolet light is an electron excited from the HOMO to the LUMO
In an IR spectrum, how does extended conjugation of double bonds affect the absorbance band of carbonyl stretches compared with normal absorption?
The absorbance band will occur at a lower wave number carbonyl groups in conjugation with double bonds tend to absorb at lower wavenumbers because the delocalization of pi electrons causes it to lose its double bond character, shifting the frequency closer to a single bond between a C-O side of the spectrum. So a loss of double-bond character should decrease the absorption frequency of the group.
What is the equation for collision theory?
The arrhenius equation which is: Ae^(-Ea/RT) = k
One student does not pay attention during their pre-lab meeting, and chooses to use an indicator that has a pKa more than seven units away from that of the weak acid used in their titration. How will this affect the equivalence point and end point of the reaction?
The end point will now occur significantly after the equivalence point
Explain the difference between the equivalence point and end point, focusing on the volume difference needed to achieve both.
The equivalence point is where all of the titrand has reacted, whereas the end point is later, once the titrant is reacting with the indicator. If you picked a good indicator though, the difference in volume should be negligible!
A company always uses the same analyte, a weak basic solution of 0.2 M pyridine. (pKb = 5.21) with pH of 9.3. One potential indicator compounds has been found to be a stronger base than the analyte being used, with a pKb of 3.14. This indicator is normally colorless, but turns blue when it is protonated. What does this mean for the experiment?
The indicator will react with the analyte immediately, changing color without the titrant being added We can figure out that the pKa is 11, so the indicator should change colors when the pH of the solution is near or below 11. (think of the weak base titration graph, its decreasing, so once it gets below 11, the indicator will react) Therefore the indicator should react immediately when added to the analyte solution bc the pH is 9.3.
Why does the ion move in a circle in mass spec.?
The ion moves in a circle because the magnetic force is perpendicular to the velocity of the ion, pointing toward the center of the circle. The magnetic force essentially acts as a centripetal force.
What is the work function?
The minimum energy needed by an electron to escape the metal surface
What is Fischer esterification?
The procedure involves a reaction of a carboxylic acid with an alcohol
The stable N/Z ratio for large atoms (Z > 83) is greater or less than that of small atoms? Why?
The stable N/Z ratio for large atoms is greater than that of small atoms. This is due to the fact that once you add more nucleons to a nucleus, the protons on opposite ends of the nucleus will not experience the strong nuclear force; thus, protons will be more repelled from one another, resulting in less protons per neutrons in the nucleus.
compare the titrant to the titrand
The titrant is the small pipette we are adding to the solution the titrand is the known volume solution of unknown concentration
What does it mean when a carbonyl is unsaturated?
There is a double bond in conjugation to the carbonyl. This allows it to go through 1,2 (attacks central C) and 1,4 addition (attacks double bond)
How do aldehydes and ketones react in the presence of water?
They are hydrated and form geminal diols
Are non metals reactive?
They are not. Bc they do not have electrons moving freely
what is cellulose in chromatography?
This is what the paper is made of in paper chromatography. It is a polar substance
The Bohr model hydrogen energy levels can be described by the equation En =E1 / n^2 where E1 = -13.6 eV. A hydrogen atom absorbs a photon with an energy of 13.6 eV. What transition will the electron undergo? A: transition from n=1 to n=0 B: transition from n=infinity to n=1 C: transition from n=1 to n=infinity D: transition from n=1 to n=2
Transition from n=1 to n=infinity The energy of the n=1 level is a negativve value representing how much energy it would take to remove that electron from the atom. If the electron absorbed that much energy, it would jump to the n=infinity level and ionize the atom
What is transesterification?
Treatment of an ester with an alcohol under acid catalyzed conditions (just makes a different ester based on the alkyl gruop of the alcohol).
True or false? All spontaneous reactions are irreversible.
True
True or false? At the equivalence point, there is no buffering capacity because the titrand (what the titrant is being added to) has fully reacted with the titrant.
True. At the equivalence point, there is no buffering capacity because the titrand (what the titrant is being added to) has fully reacted with the titrant.
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.
What is the Rydberg unit of energy?
True. The Rydberg unit of energy is equal to 2.18 ⋅ 10 ^-18 J/electron, and is the experimentally determined energy of an electron at the smallest possible orbital.
True or false? When looking up enthalpy values for a set of reaction species, the enthalpy depends on the concentration of the species.
True. The enthalpy depends on the concentration of the species.
What does TLC often used? (thin-layer chromatography)
Uses a silica gel which is polar and hydrophilic. So the more nonpolar the substance is, the further it will move up the plate
what is methylene chloride?
a carbon attached to 2 Cl's. This substance is non polar
What is the Jones oxidation?
We use an even stronger chromium containing oxidizing agent called CrO3. When dissolved with dilute sulfuric acid in acetone, they will also turn primary alcohols into carboxylic acids and secondary alcohols to ketones
How would you protect a ketone or aldehyde from reacting with LiAlH4?
We would react it with a diol forming an acetal or a ketal.
What is autoionization?
When two identical molecules of an amphoteric compound react with each other, with one acting as an acid and the other acting as a base
compare imine and enamine structures
iminie has a C==N and an enamine has a C==C with a N bonded to it as well
What is a quinone?
When you treat a phenol with an oxidizing agent. They are resonance stabilized electrophiles.
What happens if you want to do a titration and dont know the pKa of the weak acid in the solution?
Would need a computer program that graphs it for you and a pH meter. cant figure it out another way
Can you make a buffer with a weak acid and strong base? How?
Yes. We will add half as much strong base. The weak acid will then react and the conjugate base is formed
What is the pH of a .76 M solution of 173.8 mL acetic acid (Ka = 1.8 ⋅ 10^-5) after the addition of 17.4 mL of .23 M NaOH? (A) 1.23 (B) 3.42 (C) 5.32 (D) 7.53
You can use the HH Equation here if you'd like, but I would just think it through as follows (otherwise it will take you many more steps): "There is more than 10x but less than 100x of the conjugate acid than the conjugate base; therefore, the pH must be between 1 and 2 pH units below the pKa of acetic acid (4.75). My answer must be around 3.
What would happen if you oxidize a tertiary alcohol?
You can't do it. You would have to break a c-c bond which is not favorable.
How do you turn on acetal or ketal back into a carbonyl? (remove the PG)
You had a catalytic acid which usually looks like cat. H+
How do you turn a primary alcohol into an aldehyde?
You have to oxidize it with PCC. any other oxidizing agent will turn it into a carboxylic acid
What simple equation illustrates the relationship between effective nuclear charge (Zeff) and electron shielding?
Zeff = Z (nuclear charge) - S (electron shielding)
Which of the following ions would be least deflected in a mass spectrometer? A: Zn2+ B: Fe2+ C: Al3+ D: Ca2+
Zn2+ bc it has the the highest mass-to-charge ratio. Al3+ has the lowest. The amount of deflection is inversely proportional to the mass-to-charge ratio
NH3 forms a complex ion with Ag+. Two solutions, a pure water solution and a 3 M NH3 solution, have AgCl dissolved to the point of saturation. How do the concentrations of Ag+ and Cl- compare between the solutions?
[Ag+] is greater for the pure water solution; [Cl-] is greater for the NH3 solution The formation of the complex ion removes Ag+ from the solution (it is locked up in the complex ion). This reduces [Ag+] for the NH3 solution, which allows more AgCl to dissolve. Overall, this increases the [Cl-] as the [Ag+] concentration goes down.
From the electronic configurations given below, which element is most likely to act as an oxidizing agent? [Ar]4s23d104p6 [Ar]4s23d10 [Ne]3d9 [Ne]3s1
[Ne]3d9 Remember, the 3s1 will want to LOSE an electron bc it is an alkali metal
what is silica gel? What substances will adhere to the gel?
a highly polar substance. this means than any polar compound will adhere to the gel and this move through (elute) slowly
What is the constant J
a measure of degree of splitting caused by other atoms in the molecule
due to the aciddity of the alpha hydrogen, aldehydes and ketones exist in a solution as....
a mixture of two isomers in keto and enol
what is an aldol?
a molecule that contains both aldehyde and alcohol functional groups
what is brine?
a solution of sodium chloride in water (salt water)
What is a zwitterion?
a zwitterion is a species with both a positive and a negative charge (dipolar ions). When an amino acid is put into a solution, it will take on both charges bc it is amphoteric
what is electron capture?
capture an electron, convert a proton to neutron
what is phthalimide?
acts as a nucleophile in the gabriel synthesis
A solution is saturated with CaCO3, with solid CaCO3 in the bottom of the solution. What can be done to dissolve more of the solid CaCO3? stir the solution decrease the temperature add CaCl2 Add HCl
add HCl adding HCl would increase the H+ concentration and it will react with CO3(2-) to form HCO3- and H2CO3 bc of the bicarbonate system. This reduces the CO3(2-) concentration in the solution which will move the dissolution reaction forward
Compare physcial propertires of ketones and aldehydes vs alcohols (BP and better electrophile and more polar dipoles)
alcohols will have higher BP bc of H-bonds. Ketones and aldehydes have more polar dipoles, most common electrophile. aldehydes even more so bc of less sterics
the pH ranges the methyl red, bromothylmol blue, and phenolphthalein are 4.4-6.2, 6.0-7.6, and 8.2-10
all 3. bc the titration curve for a strong acid and strong base is so steep and covers so many pH units, any of the three indicators could be used for this titration
beta lactams are: I. cyclic forms of the least reactive type of carboxylic acid derivative II. more reactive than their straight-chain counterparts III. molecules with high levels of ring strain
all of the above lactams are amides in the the form of 4 membered rings; amides are generally the least reactive type of carboxylic acid derivative. B lactams experience significant ring strain from both eclipsing interactions (torsional strain) and angle strain, and are therefore more susceptible to hydrolysis than the linear form of the same molecule
3 main examples of nucleophiles
anions, pi bonds, and atoms with lone pairs
What is the Gabriel synthesis?
another way of synthesizing an amino acid
Would acid dissolve better in aqueous acid or aqueous base?
aqueous base bc it will become more highly charged as it dissociates to form the conjugate base
Henrys law main idea
as partial pressure of gas above solution increases, the solubility of that gas will increase
compare nucleophile stregnth and base strength with kinetic property and thermodynamic property
base strength is thermodynamic property. nucleophile strength is kinetic property
what are dimer? what tend to form these?
carboxylic acids tend to form this. these are pairs of molecules connected by two hydrogen bonds.
What is NMR spectroscopy?
based on fact that certain atomic nuclei have magnetic moments that are oriented at random. They can either be with or against the direction of the applied field. the alpha state is low energy and is with the field. Beta state is higher energy. It is plotted as frequency vs. absorption. Helps us figured out the arrangement of functional groups
What is ion exchange chromatography?
beads are coated with charged substances to bind compounds with opposite charges
What is size-exclusion chromatography?
beads have small pores which trap smaller compounds and allow larger compounds to travel through much faster.
Which is more soluble in water... H2 or CO2?
both are noon polar, CO2 at least has polar bonds
why can a protic solvent hinder a nucleophile?
by protantating the nucleophile or through H-bonding. The further you go down the periodic table, the less likely the nucleophile is to be affected by protonation because they are typically stronger acids such as HI instead of HF.
how are anhydrides produced?
by the rxn of two carboxylic acids with the loss of a water molecule
What is TMS in NMR?
calibration standard to mark 0 ppm.
what are geometric isomers?
cis-trans isomers
What is affinity chromatography?
column is made to have high affinity for a compound by coating the beads with a receptor or antibody to the compound
what does n= infinity represent?
complete ionization of the hydrogen atom, where the electron is no longer orbiting the atom
What is opposite of common ion effect?
complex ions stablize the dissolution and has very high Ksp values
What is a mesylate?
compound containing functional group -SO3CH3. Used to protonate a hydroxyl group to make it a better LG for nucleophilic substitution rxn and can also serve as a PG.
How do you form an anhydride?
condensation of two carboxylic acids. (nucleophilic acyl substitution)
differentiate conformational isomers (conformers) and configurational isomers
conformational isomers are same molecule, only at different points in their natural rotation around a single sigma bond. (newman projection) configurational isomers can be interconverted only by breaking bonds. include enantiomers and diastereomers
What is UV spectroscopy used to detect?
conjugaed alkenes
What is an enone?
conjugation with a carbonyl group
what is the system for labeling optical activity?
d- (+) refers to clockwise. l- (-) refers to counterclockwise. Cant be determined from the molecule. Must be determined experimentally
What would be the effect on the Rf values if TLC were run with hexane rather than ether as the eluent?
decrease. Since hexane is less polar, it is less likely to displace polar compounds adsorbed to the silica gel. This would decrease the distance these polar compounds travel, decreasing the Rf values. This is why the organic solvent is usually of weak to moderate polarity.
In aqueous solution, pyrophosphate will likely:
degrade into inorganic phosphate this is bc pyrophospahte is unstable in aqueous solution.
Each of the following reaction types occurs during the gabriel synthesis except: A. decarboxylation B. Nucleophilic substituion C. Dehydratoin D. Hydrolysis
dehydratoin hydrolysis and decarboxylation both happen at the end
2 equations that relate delta G with 1) Q and Keq 2) G^o and Q
delta G = RTln(Q/Keq) and delta G = delta G^o + RTlnQ
electrochemistry equation for G^o and E^o
delta G^0 = -nFE^o
How does G^o relate to Keq
delta G^o = -RTlnKeq
what does Keq depend on in electrochemistry?
depnds on identity of electrode and temp
Purpose of mass spectromter?
determine mass of an atom
what has suffix of -dioic acid?
dicarboxylic acids
What do Lyman, Balmer, and Paschen series have to do with anything?
different groups of hydrogen emission lines correspond to transitions from energy levels: L = all B = All except 1 P = all except 1,2
two aldehydes can react with each other to form an alcohol and a carboxylic acid. This is an example of: elimination reaction combustion reaction acid-base reaction disproportionation reaction
disproportionation reaction
compare eclipsed and totally eclipsed (newman projection)
eclipsed is when they all overlap but two largest groups are 120 degrees apart. totally eclipsed in when two largest groups are right on top of each other, this is the highest energy state
what is the eluent and absorbent in gas chromatography?
eluent is a gas (usually He or N) absorbent is crushed metal or polymer inside the column
What is positron emission?
emission of a positron when a proton becomes a neutron. the opposite of beta decay
What is the Henderson-Hasselbach equation used for?
estimate pH of a buffer solution
percent error equation
experimental value-accepted value/accepted value x 100
True/False Strong electrolytes are solutes that will dissociate completely in any solvent.
false. they do not necessarily have to be soluble in any given solvent
what drives the separation in chromatography?
fight between stationary phase (absorbent) and mobile phase. We run the molible phase through the stationary phase. Depending on their characteristics, each substance will migrate at different speeds. (polarity is mostly the property that affects separation)
what is the strecker synthesis used for?
for making amino acids out of an aldehyde(or ketone), ammonium chloride, and potassium cyanide. Has an imine in the mechanism
In the hydrolysis of salts, a cation and anion are freed and can interact with water. Which of the following salts, when dissolved in water, will make a solution with a pH of 7? CuCl2 MgCl2 NaNH2 Fe(NO3)3
for the solution to still have a pH = 7, that means that both the cation and anion formed in the rxn must not react with water. Copper and iron are both stronger acids than water and NH2- is a stronger base than water. Mg is a large group 2 element and will not react with water. Chloride is the conjugate base to a strong acid so it wont either.
An emission spectrum has a line at 656 nm that involves the n = 2 and n = 3 energy levels. The spectrum also has a line at 486 nm. Which of the following is a possible transition for this line? A: from n=2 to n=4 B: from n=3 to b=4 C: from n=4 to n=2 D: from n=4 to n=3
from n=4 to n=2 656nm is part of the emission spectrum so light is being emitted, or energy is being given off. This means the transistion must be from a higher energy level to a lower energy level. 486 nm is highr in energy than 656nm so must have a greater energy difference.
compare gauch with anti conformation (newman projection)
gauche means two large groups are 60 degrees apart. Anti means that two largest groups are on opposite sides, most energetically favorable
difference between geminal and vicinal?
geminal means on the same carbon. vicinal means on nearby carbons
compare gravity filtration and vacuum filtration
gravity filtration is when the solvents own weight will pull it through the filter. used when the product of interest is in the liquid. vacuum filtration is when the solvent is forced through the filter by a vacuum connected to the flask, mostly used when solid is the desired product.
how great does difference in electronegativity need to be for it to be an ionic bond?
greater than 1.7
How might succinic anhydride, show below, be formed from succinic acid (butanedioic acid) Catalytic acid Catalytic base Heat Oxidation
heat anhydrides, particularly cyclic anhydrides, will form spontaneously from dicarboxylic acids when heated
what is the opposite of a coordinate covalent bond?
heterolytic reactions. when a bond is broken, both electrons are given to one of the two products
whats less polar hexane or ether?
hexane
What does it mean that it is not kinetically favorable?
high activation energy
Compare hydroquinones and hydroxyquinones
hydroquinone are benzene rings with two hydroxyl groups hydroxyquinones contain two carbonyls and a variable number of hydroxyl groups (making it slightly less electrophilic bc of the EDG) (can have like 3 rings together, as long as they follow the rules above)
which is thermodynamically favored, imine or enamine?
imine
what is a diol?
is when an alcohol has two hydroxyl groups, these are nucleophiles bc of the lone pairs on the oxygens. they are commonly used as protecting groups for aldehydes or ketones.
What is ubiquinone
it is coenzyme Q a biologically active quinone that acts as an electron acceptor in the ETC. It can be reduced to ubiquinol
What does it mean that the rxn is under kinetic control?
kinetic product is the major product
What quantum number represents the subshell?
l... not n!
What are cyclic amides calld?
lactams
what are esters that are cyclic called?
lactones
How you figure out the highest BP out of methanol, isobutyl, alcohol, and propanol?
longer chain = higher BP
What are the four types of vibration that can occur in an IR spec.?
look at chart
What is a volatile compound?
low melting point, sublimable solids or vaporizable liquids
Which is the symbol for the magnetic quantum number?
m(l)
Which quantum number relates to the orientation of electron orbitals? m(s) n m(l) l
m(l)
As atoms increae in atomic number, they have more and more elecrtons, each with its own unique set of quantum numbers. For which quantum number does the number of possible values not increase as the number of electrons in the ground state increases? m(s) n m(l) l
m(s)
What is infrared spectroscopy?
measures molecular vibrations. Infrared light is passed through a sample and absorbance is measured. Helps determine what bonds exist within a molecule and we hope to infer the functional groups
which has a bigger ionic radius... metals close to the metalloid line or metals further away?
metals further away than the metalloid line
What is the defining characteristric of transition metals?
metals that have an unfilled d orbital in their atomic or ionic forms
NH3 has a pKb of 4.75. Would methyl red or phenolphthalein be a better indicator for titrating NH3 with HCl, and why? methyl reds indicator is pH 4-6 pheno... indicator is pH 8-10
methyl red, because the half equivalence point overlaps with phenolphthaleins's indicator range of pH 8-10 the pKa of the conjugate acid must then be 9.75. the pKa is equal to the pH where the half equivalence point is. So pheno... will change colors at the half equivalence point which is not what we want
The gas eluent in gas chromatography and the liquid eluent in paper chromatography are examples of which component of these systems? A. Stationary phase B. Mobile phase C. Column D. Fraction
mobile phase
How do you determine number of moles deposited on plate in battery?
mol Metal = It/nF where F = 10^5 ...
how does ph relate to pka
pH = pKa + log [A-]/[HA]
compare physical and chemical properties?
physical properties are characteristics that dont chagne the composition of matter, melting point, boiling opint, solubility, odor, color or density chemical properties have to do with the reactivity with other molecules and result in changes in chemical composition. This is generally dictated by the functional group
if stationary phase is non-polar, what moves up furthest?
polar molecules
opposite of dissolution?
precipitation
What is chemoselectivity?
preferential reaction of one functional group in the presence of other functional groups
What is the Cahn Ingold Prelog priority rule?
priority for E and Z forms, as well as R and S, is based on the fact that higher atomic number is higher priority.
If propanamide were treated with water, what products would be observed? Propanamide Propanoic acid Equeal concentrations of propanamide and propanoic acid Propyl propanoate
propanamide No reaction would be observed BECAUSE cannot go up the chain. This would be making a carboxylic acid from an amide. Requires strong acid and base to undergo nucleophilic acyl substitution
protic vs aprotice solvents
protic can hydrogen bond, aprotic cant
When a bond is created between two nucleotide triphosphates in DNA synthesis, the small molecule released from this reaction is: Pyrophosphate Inorganic phosphate ATP Organic phosphate
pyrophosphate
what are two equations for heat absorbtion or release?
q=mc(delta)t for temperature raise/lower (C = constant) (m is in kg) q=mL for phase changes (L = constant) (m is in kg)
What kind of molecule displays no optical activity?
racemic mixture and meso compounds (plane of symmetry exists)
How do you turn a carboxylic acid into an amide?
react it with ammonia or an amine. (nucleophilic acyl substitution)
How to create esters from carboxylic acids?
react them with primary alcohols. (nucleophilic acyl substitution)
What is wavenumber?
reciprocal of wavelength. we measure 4000 - 400 cm^-1 on the IR spec.
What is partitioning with respect to chromatography?
rep. an eq. between the two phases. different compounds will have different partitioning coefficients and will elute at different rates.
how do you name a salt of a carboxylic acid?
replace the ending -oic acid with -oate. and say the cation first. such as sodium hexanoate
whats a risk when running affinity chromatography?
risk of rendering the substance unusable. The column often binds to the target molecule. So only choose affinity chromatography if the all others don't make sense
What is a concerted rxn?
rxn that only has one step
what can you say about how enantiomers will react?
same physical and chemical properties but they rotate plane-polarized light in opposite directions and react differently in chiral environments. (polarized light means that it got organized all in the same direction)
What is gas chromatography (vapor-phase chromatography)?
separates vaporizable compounds according to how well they adhere to the adsorbent in the column. the stationary phase is a coil of crushed metal or a polymer. The mobile phase is a nonreactive gas. often used with mass spectrometry.
what happens after common ion effect?
system will shift to the left reforming the solid salt. molar solubility for the solid is reduced and less of it dissolves. Ksp remains constant
first order half life equation
t1/2 = 0.693/k
second order half life equation
t1/2 = 1 / k[A]o
zero order half life equation
t1/2 = [A]o/2k
what is unique abut aldol condensation rxn?
the aldehyde or ketone acts both as an electrophile (keto form) and a nucleophile (enolate form)
A stable atom (Z=50) has an atomic mass of 119 amu. when this atom is placed between the two plates of a capacitor, what will be observed?
the atom will not move. it says that the atom is stable which means is it neutra. becasue of this, it will not be acted upon by the positive or negatively charged plates of the capacitor
what would we expect in a reverse aldol rxn?
the breakage of a C-C bond, forming two aldehydes, two ketones, or one of each from a single molecule
what two factors affect the amount of rotation for optical activity? What is the equation?
the concentration of the optically active compound and the length of the tube. The equation is: observed rotation/ (concentration of solution x length of tube) = specific rotation in degrees
Describe intramolecular anhydride formation
the hydroxyl group of one acts as the nucleophile, attacking the other carbonyl on the other.
what would elute the fastest in a column chromatography with ether on silica gel?
the least polar compound travels fastest
why would 1-hexanol have a higher boiling point than 1-pentanol?
the longer hydrocarbon chain has increased VDWF
what travels further up the paper in TLC and paper chromatography?
the more non polar substance
What is deshielding of a proton in NMR?
the more the proton's electron density is pulled away, the less it can shield itself from the applied magnetic field.
A student adds sodium acetate to a solution of acetic acid. What will happen to the pH and why?
the pH will increaes bc an increased concentration of acetate ions will push the acid dissociation reaction backwards
Why should esterification reactions NOT be carried out in water?
the presence of water in an esterification reaction would likely revert some of the desired esters back into carboxylic acids.
What happens when you react a strong oxidizing agent like Na2Cr2O7 or K2Cr2O7 with a primary and secondary alchohol?
the primary alcohol will become a carboxylic acid and the secondary alcohol will become a ketone.
compare relative configuration and absolute conformation
the relative configuration of a chiral molecule is its configuration in relation to another chiral molecule. we use this to determine if they are enantiomers, diastereomers, or the same molecule. Absolute conformation: uses the Cahn-Ingold-Prelog priority rules (R and S)
Why is rotation limited of a peptide bond?
the resonance gives the C-N bond partial double-bond character
what does it mean to elute the sample in chromatography?
the sample will travel through the stationary phase
what does a small Rf mean?
they are more polar since they are more attracted to the stationary phase
what do alkyl groups stabalize?
they stabilize positive charges and destabilize negative charges. they are electron donating. they will make molecules less acidic
Why do we use hot solvent in gravity filtration?
to keep the product dissolved in liquid. otherwise, the product will precipitate and be present in the residue
what are tautomers? what is tautomerization?
two isomers that differ in the placement of a proton and the double bond. the process of interconverting from the keto to the enol tautomer. Tautomers are NOT resonance structures
what is root mean square speed equation?
urms = square root of 3RT/M
what is most useful when doing adol condensation rxn?
use only one type of aldehyde or ketone to prevent a mixture of products or if one of the molecules has no alpha hydrogens
What is column chromatography?
uses polarity, size, or affinity to separate compounds based on their physical and chemical properties. the stationary phase is a column containing silica or alumina beads. mobile phase is a nonpolar solvent, which travels through the column by gravity.
What do strong acids have in terms of Ka and pKa?
very high Ka values and very low pKa values
What is spotting?
we apply a small, well defined spot of the sample directly onto the silica or paper plate.
what would we expect in a dehydration rxn?
we should release a water molecule
What happens in the retro-aldol rxn? what bond is broken? what do we use? how can it be facilitated?
we use aqueous base and heat. We break the bonds between the alpha and beta carbons. rxn can be facilitated if the intermediate can be stabilized in the enolate form (just like the forward direction)
What would we expect in an aldol condensation rxn?
we would expect to form a single product by combining two aldehydes, two ketones, or one of each
what does small Ka mean
weak acid
What is saponifcation?
when long-chain carboxylic acids react with sodium or potassium hydroxide. a salt is formed (soap). When we place it in an aqueous solution, micelles will form and nonpolar hydrocarbons on the inside can dissolve molecules like grease - process by which fats are hydrolyzed under basic conditions to produce soap
Generally, what is the typical range from which the indicator will have its color change?
when pH = pKa +/- 1
What is hydration?
where water molecules surround dissolved ions and molecules
Are nitrate, perchlorate, and acetate salts soluble?
yes
osmotic pressure equation and units of each
Π = iMRT; Π = Osmotic pressure; (atm) i = # of molecules obtained from solvation; M = Molarity; R = Ideal gas constant; (.082) T = temprature (kelvin)
