Chemistry Section 1 (Altius MCAT Prep)
What is a neutron?
neutron = proton + electron
AgI
silver iodide
Hydroxide
OH−
How do you name monatomic ions?
Replace the last syllable with "ide" (sulfide ion, hydride ion, chloride ion)
Sulfate
SO4^2−
H2SO4
Sulfuric Acid
What is the bond length?
The distance between the nuclei of the atoms forming the bond
Chemical equilibrium
The forward rate of reaction equals the backward rate of reaction. Equilibrium does not mean the reaction has stopped only that the forward rate and backward rate has become the same.
Cu(CN)2
copper(II) cyanide
HCl (g)
hydrogen chloride
Pb(NO3)2
lead(II) nitrate
How do you name Ionic Compounds?
Name the cation first and then the anion. (calcium sulfate is CaSO4 not SO4Ca)- duh
NaHCO3
sodium bicarbonate or sodium hydrogen carbonate
Na2CO3
sodium carbonate
H2SO3
Sulfurous Acid
Non- Metals
Think of non-metals as smaller atoms with tightly held electrons. Non-metals form negative ions, have lower melting points than metals, and form covalent bonds with non metals. Most of the O-chem stuff involves non-metals.
actual yield
This is how much you actually yield
N2O
dinitrogen monoxide
LiF
lithium fluoride
Define Molarity
(moles of solute)/(L of solution)
What element in its ground state will have the same electron configuration as a chloride ion? (Cl 1-)
1s2 2s2 2p6 3s2 3p6 (same as Ar & same as Ca 2+)
What is the electron configuration of calcium in calcium sulfate? (Ca 2+)
1s2 2s2 2p6 3s2 3p6 (same as Ar & same as chloride ion)
Which orbital is higher in energy, a 4p or a 5s? What about a 3d and a 4s?
5 s orbital has higher energy. 3 d orbital has higher energy. The order of increasing energy for orbitals within a given principal energy level is s < p < d < f < ... This trend results from the fact that s orbitals have a greater electron density near the nucleus than p orbitals, and p orbitals have greater electron density near the nucleus than d orbitals. In a many-electron atom, the energies of the orbitals increase as follows 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s ... Note also that the higher principal energy levels (n values) have more subshells, and as these split in energy some of these subshells can actually be lower in energy than subshells from a lower principal energy level. Thus the energy of a 4s orbital is very close to the energy of a 3d orbital in a many-electron atom. In potassium and calcium atoms the energy of the 4s orbital is less than the energy of the 3d orbital.
Reactions What is a decomposition reaction?
A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form: AB ---> A + B
Mole
A mole is defined as Avogadro's number of anything.
Avogadros Number
A mole is defined as Avogadro's number of anything. Just as a dozen is defined as 12 of anything, a mole is 6.022 x 10^23 of anything. You can have a mole of atoms, molecules, cars, monkeys, whatever.
Electron Capture
A proton is changed into a neutron via electron capture. This occurs in both electron capture and positron emission.
Positron Emission
A proton is changed into a neutron w/ expulsion of a positron. A proton being changed to a neutron occurs in both electron capture and positron emission.
Sn(OH)2
tin(II) hydroxide
Describe Ionic character.
All bonds that are not between two atoms of the same element have some ionic character. It is basically a measure of the polarity of the bond. Ionic species such as NaCl have close to 100% ionic character. Covalent bonds between two non-metals of nearly identical electronegativity have close to zero ionic character. Ionic character is greatest when the two elements involved have the greatest difference in electronegativity and is lowest when they are the most similar in electronegativity.
State whether the following will increase or decrease as you go across a period or down a group of the periodic table: electron affinity, electronegativity, ionization energy, atomic radius and metallic character.
Atomic Radius: DOWN a Group: Atomic radius INCREASES as you go DOWN a Group because each successive Period (row) has an additional occupied energy level. If you visualize the not 100% accurate but still useful Bohr model of the atom, you can think of it this way: each time you drop down a row, you add a "ring." ACROSS a Period: Atomic radius DECREASES as you go ACROSS a Period because the net nuclear charge increases (Huh?). Remember, it's the protons (+) in the nucleus that pull on or attract the electrons in the orbitals. Across a Period you are adding more and more protons pulling on electrons occupying the same orbitals. The overall effect is more pulling power in the same basic space. This draws the electrons in closer, making the overall atomic radius smaller at the right side of a Period. Ionization Energy: DOWN a Group: Ionization energy DECREASES as you go DOWN a Group because the farther the valence electrons are from the nucleus (pulling power of the protons) the less energy it costs another atom to steal them. ACROSS a Period: Ionization energy INCREASES as you go ACROSS a Period because atoms are getting ever closer to that magic "octet" rule for stability via the Noble Gas configuration. In plain speak - your frequent buyer punch card gets one step closer to the freebie each time you move closer to the right of the Periodic Table so you guard those punches more carefully. The atomic radius is getting smaller, too, so those protons do a great job of holding on tighter. Electron Affinity: DOWN a Group: Electron Affinity DECREASES (a tiny bit) as you go DOWN a Group because elements become slightly less attractive toward electrons. Father from the pull of those protons, remember? ACROSS a Period: Electron Affinity INCREASES as you go ACROSS a Period because generally speaking (and remember, exclude the Noble Gases here) elements toward the right of the Periodic Table give off a great deal of energy when they gaining electrons to become more stable. Electronegativity: DOWN a Group: Electronegativity DECREASES as you go DOWN a Group because the valence electrons are increasingly farther away from the attraction of the protons in the nucleus. Less pull, less "desire" to grab other electrons. ACROSS a Period: Electronegativity INCREASES as you go ACROSS a Period because the number of protons (+ charges) in the nucleus increases. More protons in the nucleus means electrons are more strongly attracted to the nucleus. Chemical Reactivity: METALS DOWN a Group: In METALS reactivity INCREASES as you go DOWN a Group because the farther down a Group of metals you go, the easier it is for electrons to be given or taken away, resulting in higher reactivity. ACROSS a Period: In METALS reactivity DECREASES as you go ACROSS a Period because though they still want to give away valence electrons they have more of them to get rid of, which requires more energy. Not as easy to blow off a little steam! NON-METALS UP a Group: In NON-METALS reactivity INCREASES as you go UP a Group because the higher up and to the right atoms are, the higher the electronegativity, resulting in a more vigorous exchange of electrons. Fluorine? A greedy, impatient beast when it comes to electron exchange manners. ACROSS a Period: In NON-METALS reactivity INCREASES as you go ACROSS a Period because (notice how trends repeat?) the closer you get to fulling your s- and p- orbitals the more motivated you are to do so.
Why do bonds form? Is energy required or released when a bond is formed?
Atoms are with out feelings and don't "want" to form bonds. They only do so in situations where the resulting bond is a lower energy state than was the unbonded form (or than the previous bonds they were engaged in with other atoms). As a result, forming bonds always releases energy. This is a major point of confusion for students. ATP is often the molecule that exacerbates this confusion. The transition from ATP to ADP does release energy, but only because the forming of the new bonds in ADP releases more energy than was required to break the bonds in ATP—NOT because breaking the bonds in ATP released energy.
A certain metal is known to have a work function of 500J. If a photon of 500J strikes the surface of the metal, what will be the result?
Because the energy of the photon exactly equals the work function nothing will happen. Theoretically, it is as if the electron is now "freed" from its attraction to the nucleus but cannot move because it lacks any excess energy to transfer into KE.
Energy Levels & Photon-Light Emission What happens when energy is added? Released?
Because they are quanitized, you cannot cause an electron to move up one energy level until you add an amount of energy just greater than the difference in energy between the two energy levels. If an excess energy is added, but not enough of cause the electron to jump two energy levels, the electron will only jump one level and the excess energy will be released. If an electron drops one energy level, energy is released as a photon or as electromagnetic radiation. The energy released will be exactly equal to the difference in the two energy levels. Valence electrons cannot move up any further, but can be ejected.
HCO3-
Bicarbonate
Explain bonding vs anti-bonding orbitals.Which is higher in energy- bonding or anti-bonding orbitals?
Bonding orbitals contain electrons that are "in phase" and are said to be attractive. Anti-bonding orbitals are said to be "out of phase" electrons and are repulsive. The bonding orbitals are at a lower energy than the anti-bonding orbitals, so they are the first to fill up.
Cyanide
CN−
Carbonate
CO3^2−
H2CO3
Carbonic Acid
Chlorite
ClO2^−
Chlorate
ClO3^-
Perchlorate
ClO4^-
Hypochlorite
ClO^−
Coordination bond
Coordination compounds, a.k.a. coordinate covalent bonds, are bonds in which one atom donates BOTH of the electrons necessary to form a sigma bond. This usually occurs between a transition metal with a positive oxidation state and an atom containing a lone pair. Multiple NHR3 bonded to a transition metal is probably the most common one you will see .
Explain ionic vs covalent bonds
Covalent bonds are usually formed between two non-metals and involve sharing of electrons within the bond. This sharing need not be equal, and is in fact usually not due to differences in electronegativity. Electrons are only rarely shared equally in a covalent bond. For this to occur the two atoms involved must have identical electronegativities. Ionic bonds are usually formed a between a metal and a non-metal and are due to an electrostatic attraction. They can be conceptualized in two ways. First, you can visualize the two species as previously formed ions. For example, Na+ and Cl-. It is fairly obvious that these two species will be strongly attracted to one another by an electrostatic force. Alternatively, you can also visualize it as if the two atoms came together in their ground states (not as ions) and the more electronegative atom (Cl- in this case) pulled one electron completely away from sodium. This would result in essentially the same result, a sodium cation and a chloride anion.
What makes a good electrolyte?
Covalent compounds that dissociate 100% in water (like strong acids and strong bases). Other covalent compounds are normally bad electrolytes. -Ionic compounds that are soluble in water always make good electrolytes! Ionic compounds, they do conduct electricity well when dissolved in solution, but covalently bonded pairs such as HCl also do this when dissolved in solution. Essentially all ionic compounds are solids at room temperature. You may note that there are covalent compounds that are also solids at room temperature but not all.
Beta Decay
During beta decay a neutron is changed into a proton with the associated loss of an electron. ***So you GAIN a PROTON!!!!!***
E=hf what are the variables and in which equation would you manipulate it in?
E is the energy of a photon, h =Planck's constant and f=frequency. KE= E-Φ
Derive an equation that would allow you to calculate the Energy of a photon knowing only velocity and wavelength
E=hf f=velocity/wavelength E= hv/λ or (Plancks)(velocity)/(wavelength) Solve v = fλ for f to get: f = v/λ. Substitute this for frequency in the above equation to get E = hv/λ, often written as E = hc/λ.
Definition of Energy Levels.
Energy levels are the differences in energy among the various electrons in an atom. THEY ARE QUANITIZED!- look like stair steps, not ramp- you can be in energy level 1 or 2, but never between
How does each of the following affect equilibrium: addition of a catalyst, increased temperature, lowering the activation energy, stabilizing the transition state, addition of reactants/ products?
Equilibrium constants aren't changed if you add (or change) a catalyst. The only thing that changes an equilibrium constant is a change of temperature. Equilibrium constants are changed if you change the temperature of the system. Kc or Kp are constant at constant temperature, but they vary as the temperature changesThis is typical of what happens with any equilibrium where the forward reaction is exothermic. Increasing the temperature decreases the value of the equilibrium constant. Where the forward reaction is endothermic, increasing the temperature increases the value of the equilibrium constant. Equilibrium constants aren't changed if you change the concentrations of things present in the equilibrium. The only thing that changes an equilibrium constant is a change of temperature. The position of equilibrium is changed if you change the concentration of something present in the mixture. According to Le Chatelier's Principle, the position of equilibrium moves in such a way as to tend to undo the change that you have made. Suppose you have an equilibrium established between four substances A, B, C and D. According to Le Chatelier's Principle, if you decrease the concentration of C, for example, the position of equilibrium will move to the right to increase the concentration again.
Write the balanced reactions for the combustion of Ethane
Ethane: 2C2H6 + 7O2 → 6H2O + 4CO2
What is the electron configuration of Fe2+
Fe2+: 1s2 2s2 2p6 3s2 3p6 3d6
What is the electron configuration of Fe3+
Fe3+: 1s2 2s2 2p6 3s2 3p6 3d5
What is the electron configuration of Fe
Fe: 1s2 2s2 2p6 3s2 3p6 4s2 3d6
Acids
Follow the "ate- ic -- ite-ous" convention. If the ion name ends in "-ate", replace the ending with "-ous" as in: Nitrite --> Nitric Acid. If the ion name ends in "ite" , replace that ending with "ous" as in: Nitrite --> Nitrous Acid. If the parent is a single ion rather than a polyatomic ion, replace the "ide" ending with "-ic" and add "Hydro-" as a prefix, as in: Iodide --> Hydroiodic Acid.
Gamma Emission
Gamma rays are usually emitted a s byproduct of the types of decay. Gamma decay does not change the number of nucleons!
Bicarbonate
HCO3^−
The Work Function- Explain.
If you bombard certain metals w/ energy, you can cause the ejection of an electron from their outermost shell (valence). The amount of energy required to do this is called the "work function" and is usually given the variable Φ. Not the same as ionization energy- Ionization energies are measure for lone atoms in gaseous states. The work function refers specifically to valence electrons being ejected from the surface of a solid metal. If you add less energy than the work function, the electron won't be ejected. If you add more energy, the excess energy is transferred into the kinetic energy of the ejected electron.
Which two elements in the periodic table, if united in a bond, would create a bond w/ max possible ionic character?
Ionic character is due to a difference in electronegativity between the two atoms in a bond. So, a C-C bond, for example, would have zero ionic character. Theoretically, the greatest possible ionic character would exist in francium fluoride. However, francium is extremely unstable with a half-life of around 20 minutes. It also happens to be among the rarest of all elements, so it is unlikely that francium-fluoride has ever been formed.
Ionization energy
Ionization energy is a measure of the energy needed to pull a particular electron away from the attraction of the nucleus. A high value of ionization energy shows a high attraction between the electron and the nucleus.
What is an isotope?
Isotopes are atoms with the same number of protons , but differing numbers of neutrons . Isotopes are different forms of a single element . Examples: Carbon 12 and Carbon 14 are both isotopes of carbon , one with 6 neutrons and one with 8
Equation that relates work function. What are the variables?
KE= E-Φ E is the amount of energy added and KE is the kinetic energy of the ejected electron.
What happens to Keq when you disrupt equilibrium?
Keq will not change unless you change temperature The reaction Quotient will change, however.
Provide conceptual definitions for, and clarify the difference between kinetics and thermodynamics
Kinetics is about the reaction rate; how fast are things working out? Thermodynamics is about the potential reactivity; to decide whether it would work out or not Kinetics: rate, catalysts, enzymes, energy of activation, reaction order, and transition state Thermodynamics: Keq, Q, entropy, enthalpy, Gibbs free energy, "favorability", "spontaneity" Only thing that repeats is the temperature
When you disrupt the equilibrium, creating a "shift" according to the Le Chatelier's principle what happens to Keq? Does it change?
Le Châtelier's principle states that if the system is changed in a way that increases the concentration of one of the reacting species, it must favor the reaction in which that species is consumed. In other words, if there is an increase in products, the reaction quotient, Qc, is increased, making it greater than the equilibrium constant, Kc.
Metals form ______, but non-metals form ______?
Metals form cations, but non-metals form anions. Metals tend to give up electrons and form cations. Non- metals tend to accept electrons and form anions.
Why do Metals have higher boiling and higher melting points?
Metals have high melting and boiling points because in metals there is a very strong intermolecular force of attraction and it needs a lot of energy to melt or to boil.
Write the balanced reactions for the combustion of methane.
Methane: CH4 + 2O2 → 2H2O + CO2
What is the electron configuration of Mg2+
Mg2+: 1s2 2s2 2p6
Manganite
MnO(OH)
Manganate
MnO4^2−
Permanganate
MnO4−
Ammonia
NH3
Ammonium
NH4^+
Nitrite
NO2^−
Nitrate
NO3^-
What is the electron configuration of Na+
Na+: 1s2 2s2 2p6
How do you name a binary compound?
Name the element furthest down and to the left on the periodic table first (most metallic?); use poly prefixes as necessary ( Nitrogen Trioxide, Carbon Monoxide, Sulfur Dioxide, etc). Some have common names such as ammonia and water.
Pauli Exclusion Principle
No two electrons in a single atom can have the same four quantum numbers; if n, l, and ml are the same, ms must be different such that the electrons have opposite spins, and so on.
Phosphate
PO4^3−
percent yield
Percentage Yield = (Actual Yield)/(Theoretical Yield) x 100% Recall that yield can be increased by removing product as it is formed. Overall amount of product can be increased (sometimes called yield), but % yield CANNOT be increased, by adding more reactants. Of course, if one reactant is in excess and one is limiting, then only adding the limiting reagent will have any effect.
Identify the following referring to the periodic table: period, group/family, alkali metals, alkaline earth metals, transition metals, lanthanides, actinides, halogens, noble gases, s-block, p-block, d-block and f-block.
Period: Are arranged horizontally across the periodic table (rows 1-7). These elements have the same valence shell. Group/family: Are arranged vertically down the periodic table (columns or group, 1- 18 or 1-8 A,B). These elements have the same number electrons in the outer most shells, the valence shell. Alkali metals: The alkali metals, found in group 1 of the periodic table (formerly known as group IA), are very reactive metals that do not occur freely in nature. These metals have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements. As with all metals, the alkali metals are malleable, ductile, and are good conductors of heat and electricity. The alkali metals are softer than most other metals. Cesium and francium are the most reactive elements in this group. Alkali metals can explode if they are exposed to water. The Alkali Metals are: Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium. Alkaline earth metals: The alkaline earth elements are metallic elements found in the second group of the periodic table. All alkaline earth elements have an oxidation number of +2, making them very reactive. Because of their reactivity, the alkaline metals are not found free in nature. The Alkaline Earth Metals are: Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium. Transition metals: The 38 elements in groups 3 through 12 of the periodic table are called "transition metals". As with all metals, the transition elements are both ductile and malleable, and conduct electricity and heat. The interesting thing about transition metals is that their valence electrons, or the electrons they use to combine with other elements, are present in more than one shell. This is the reason why they often exhibit several common oxidation states. There are three noteworthy elements in the transition metals family. These elements are iron, cobalt, and nickel, and they are the only elements known to produce a magnetic field. Lanthanides and actinides: The lanthanides and actinides form a group that appears almost disconnected from the rest of the periodic table. This is the f block of elements, known as the inner transition series. This is due to the proper numerical position between Groups 2 and 3 of the transition metals. Halogens: The halogens are five non-metallic elements found in group 17 of the periodic table. The term "halogen" means "salt-former" and compounds containing halogens are called "salts". All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. The halogens exist, at room temperature, in all three states of matter: Solid- Iodine,Astatine Liquid- Bromine Gas- Fluorine, Chlorine The Halogens are: Fluorine Chlorine Bromine Iodine Astatine Noble gases: The six noble gases are found in group 18 of the periodic table. These elements were considered to be inert gases until the 1960's, because their oxidation number of 0 prevents the noble gases from forming compounds readily. All noble gases have the maximum number of electrons possible in their outer shell (2 for Helium, 8 for all others), making them stable. Helium, Neon, Argon, Krypton, Xenon, and Radon. s-block: First two groups of the periodic table -- alkali metals and alkaline earths p-block: Last six element groups of the periodic table, excluding helium. The p-block elements include all of the nonmetals except for hydrogen and helium, the semimetals, and the post-transition metals. d-block: Transition metals of element groups 3-12. f-block: Inner transition elements, usually the lanthanide and actinide series, including lanthanum and actinium.
Which requires the most oxygen to combust, propane, propanol or propanoic acid?
Propane (C3H8) = 3 points for carbon Propanol (C3H8O) = 2.5 points ( 3 - 0.5 = 2.5). 3 points for carbon and 0.5 for oxygen. Propanoic acid (C3H6O2) = 2 points ( 3 - 1 = 2). 3 points for carbon and 1 point for oxygen because we have two oxygens so (0.5 + 0.5 = 1). Propane will require the most oxygen to combust. Add 1.0 for each carbon and subtract 0.5 for each oxygen. The species with the lowest total will require the least oxygen and the one with the highest total will require the most. This is not however, the actual number of moles required. The only way to determine the exact moles of oxygen required is to write out and balance the combustion reaction. REMEMBER that water is never combustible.
Write the balanced reactions for the combustion of propanol.
Propanol: 2C3H8O + 9O2 → 8H2O + 6CO2.
Define Radioactive Decay.
Radioactive decay is the process by which atoms change their chemical composition over time. They sometimes lose or gain electrons, lose bundles of protons and neutrons (alpha particles) or even transform one subatomic particle into another
What is bond dissociation energy?
Same as bond energy!- the amount of energy required to break or dissociate bonds
What is the expected condosity of 3M LiCl?
Sodium is more metallic than lithium, so we would expect an NaCl solution to conduct electricity better than an equimolar LiCl solution. This means the NaCl solution would need to be less concentrated in order to conduct equally as well. This predicts a condosity of something less than 3.0 for a 3.0M LiCl.
LeChatelier's principle
Systems already at equilibrium that experience change will shift to reduce the effects of that change. The action that will increase the pressure in a reaction vessel is any disturbance that will push the equilibrium toward the side of the reaction containing more moles of gas. So look at the side with less moles, as the side that will cause increase in pressure which will push the equilibrium towards the side with more gas (more moles).
What is the heat of combustion?
The amount of energy released when a molecule is combusted with oxygen. All covalent bonds are broken and reformed in a radical rxn. THE HIGHER THE HEAT OF THE MOLECULE, THE HIGHER THE HEAT OF COMBUSTION.
What is condosity?
The condosity of a solution is the concentration (molarity) of an NaCl solution that will conduct electricity exactly as well as the solution in question. For example, for a 2M KCL solution, we would expect the condosity to be something more than 2.0. Why would we expect it to be above 2.0? Because potassium is more metallic than sodium. Thus, we know that it will be a better conductor. This means that NaCl solution will have to be slightly more concentrated to conduct as well as the KCl solution. Ex. The more metallic an ion is, the better electrolyte it will be in solution, which will make it a better conductor. This tells us the potassium nitrate will be a better conductor than sodium chloride. From the condosity we know that it will take a 15.4 Molar solution of NaCl to have the same conductance as the unknown solution of KNOR3R. The molarity of the KNOR3 Rmust be less than that because potassium nitrate is a better conductor. In other words, to make the NaCl solution conduct equally well, we had to make it more concentrated to make up for the better electrolyte qualities of the potassium nitrate solution. (Had NaCl, hypothetically, been the better conductor, then we would expect to need a more concentrated solution of potassium nitrate in order to match the conductance of the NaCl solution).
Describe the Bohr model of an atom.
The electrons in free atoms can will be found in only certain discrete energy states. These sharp energy states are associated with the orbits or shells of electrons in an atom, e.g., a hydrogen atom. One of the implications of these quantized energy states is that only certain photon energies are allowed when electrons jump down from higher levels to lower levels, producing the hydrogen spectrum. The Bohr model successfully predicted the energies for the hydrogen atom, but had significant failures that were corrected by solving the Schrodinger equation for the hydrogen atom.
What is the difference in empirical & molecular formulas?
The empirical formula is the simplest formula for a compound. A molecular formula is the same as or a multiple of the empirical formula, and is based on the actual number of atoms of each type in the compound.
What is bond energy?
The energy stored in the bond. This is also the amount of energy required to break the bond. STABLE COMPOUNDS SUCH AS N2 HAVE THE HIGHEST BOND ENERGY. UNSTABLE COMPOUNDS (ATP) HAVE LOW ENERGIES. When something is said to be a high energy molecule that does NOT mean it has high bond energy! High energy molecule = unstable & requires little energy to dissociate bond.
What is Q?
The equilibrium constant can only be calculated at equilibrium. If you make the exact same calculation using concentration values taken at any point other than equilibrium the result is called the reaction Quotient, Q. If K < Q reaction will proceed to the left if K > Q reaction will proceed to the right Recall that both K and Q are ratios of products over reactants. K is the exact ratio at equilibrium and Q is the ratio taken at any point of a reaction. Because the products go in the numerator, if Q is greater than K, this means we must have more products than we do at equilibrium. If Q is less than K, this must mean we have more reactants than we do at equilibrium (because the reactants go in the denominator).
Half Life
The half life of a substance is the amount of time required for exactly one half to the mass of that substance to disappear due to radioactive decay
Alpha Decay
The loss of one He nucleus mass: 4 atomic #: 2
Heisenberg Uncertainty Principles
The more precisely one property is measured, the less precisely the other can be controlled, determined, or known. It implies that it is impossible to simultaneously measure the present position while also determining the future motion of a particle, or of any system small enough to require quantum mechanical treatment.
If an element of Fe originally at rest ejects an alpha particle with a speed of 2.0x10^5 m/s, what is the identity of the new element formed and what is its velocity?
The new particle is Cr. The momentum of the original particle is zero, so the momentum of both particles after the decay must be equal such that their vectors will cancel to zero. Therefore, we can write the equation: mv = mv. Using the mass of each particle in amu (4 for the alpha particle and 52 for Chromium) we get (4)(2 x 105) = (5.2 x 101)v. Solving for v gives approximately 1.6 x 104 m/s.
theoretical yield
The prediction of something in ideal conditions
What is the percent mass of carbon in glucose? what is the percent mass of hydrogen in water?
The total MW of glucose is 180g. The weight of the six carbon atoms in glucose is 72g. Therefore, (72/180) x 100 = 40%. The total mass of water is 18g. The mass of the two hydrogen atoms is 2g. Therefore, (2/18) x 100 = 11%.
Metals
Think of metals as larger atoms with loosely held electrons. Metals "like" to loose electrons and form positive ions. They are involved in ionic bonds with nonmetals. Metals behave the way they do for two reasons: 1) they are BIG and 2) they have low ionization energies (i.e., they lose electrons easily). Recall that the trend in metallic character follows the trend for atomic size, increasing down and to the left in the periodic table.
Reactions What is a single displacement reaction?
This is when one element trades places with another element in a compound. These reactions come in the general form of: A + BC ---> AC + B
What is a double displacement rxn or metathesis rxn?
This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form: AB + CD ---> AD + CB
Continue the street/apartment/room analogy used above to explain how many rooms there are in an s, p , d and f subshell.
Using the analogy provided, an orbital equates to a room and each room has two beds to be occupied by a maximum of two persons/electrons. There is only one room in an s subshell (studio apartment) and it can hold two electrons. There are three bedrooms in a p subshell and each bedroom can hold two electrons for a total of six. There are five bedrooms in a d subshell and each bedroom can hold two electrons for a total of ten. There are seven bedrooms in an f subshell and each bedroom can hold two electrons for a total of fourteen. Much like teenagers, electrons do NOT like to share rooms. Therefore, they will always fill empty orbitals first and only pair up inside the same orbital once it becomes necessary
Cations are smaller than their neutral counterpart and anions are larger than their neutral counterpart, why? Explain the difference in size between anions, cations, and neutral atoms.
When an element loses electrons and becomes a cation with net positive charge, the full nuclear charge remains in force and can attract the remaining electrons more effectively simply because there are fewer electrons and thus less electron-electron repulsion. Cations are smaller than their neutral counterparts just for this reason. For anions, however, adding electrons increases electron electron repulsion without a compensating increase in attraction to the nucleus. Anions are larger than their neutral counterparts as a result, and the increasing electron-electron repulsion makes it (a) difficult to stick a second extra electron onto a singly charged anion in the first place (the anion repels the second extra electron) and (b) unlikely that more than maybe two extra electrons will ever be stable when bound to any neutral atom.
How do you name compounds with transition metals?
When written in words, compounds that include transition elements must have a roman numeral showing the oxidation state of the metal (ex. iron (II) sulfate vs. iron (III) sulfate).
Intermolecular forces
Whenever you see a question about why something is a gas, liquid, solid, etc., or why it takes a lot of energy to go from one phase to another, you need to think intermolecular forces.
K eq=
[products]^x / [reactant] ^y raised to the exponents equal to its coefficient in the balanced equation NEVER INCLUDE LIQUIDS OR SOLIDS!!!
Second Quantum Number
a.k.a "l" or "the azimuthal quantum number". Gives the subshell or orbital; has values of 0, 1, 2, or 3, and from this we know the shape. 0= s ; 1 = p ; 2= d ; 3 = f
First Quantum Number
a.k.a "n" or "the principle quantum number". Gives the shell (ex. valence electrons are in the outermost "shell") and represents the relative energy of electron in that shell.
Fourth Quantum Number
a.k.a. "Ms" or "the electron spin quantum number". Gives the spin, which is either +1/2 or -1/2. Positive spin is represented by an up arrow in an electron configuration diagram and negative spin is represented by a down arrow.
Third Quantum Number
a.k.a. "ml" or " the magnetic quantum number". Gives the orbital orientation; has a value of -l to l (from the azimuthal quantum number). Designates the orientation of the subshell where an electron is most likely to be found (ex. which "dumbbell of a p subshell).
Predict the effect of doing each of the following to a reaction at equilibrium: adding/removing reactants, adding/removing products, increasing/decreasing pressure, increasing/decreasing temperature.
adding reactants ---> right adding products ---> left Increase pressure --> side with less moles Decrease pressure --> side with more moles Volume- Opposite of Pressure Exothermic (treat heat as a product) Endothermic (treat heat as a reactant)
What does it mean to shift the equilibrium?
all it means is to change the proportions of the various substances present in the equilibrium mixture (more blue squares) Recall that K is a "snapshot" of equilibrium that tells us where it is located and what it looks like. As far as the MCAT is concerned, temperature is the ONLY thing that changes K. (NOTE: Don't confuse what we said about shifting K with LeChatelier's principle. Le Chatelier's principle DOES NOT deal with moving K. It just says that K will ALWAYS be the same place and if you cause a disturbance that makes the ratio of products to reactants no longer equal to K, the reaction will proceed in whatever direction gets it back to K).
AlCl3
aluminum chloride
Element Symbol A
atomic number (the number of protons + neutrons)
Element Symbol Z
atomic number (the number of protons)
Atomic weight Molecular weight Molar Mass
atomic weight/molar mass/molecular weight as the "g/mol" measurement given in the periodic table for individual elements, or in the case of molecular weight, the sum of those measurements for all of the atoms in a molecule. It is the number you will use to convert grams of any substance into moles.
CaCl2
calcium chloride
CuBr
copper(I) bromide
Fe2O3
iron(III) oxide
Mg(OH)2
magnesium hydroxide
NO2
nitrogen dioxide
KOH
potassium hydroxide
What is a proton?
proton = neutron + positron