Chemistry MCAT Flashcards
Plank constant
6.63 x 10^(-34) m^2kg/s or Js
Speed of light in vacuum
3 x 10^(8) m/s
Avogadro’s number
1 mole = 6.022 x 10^(23) atoms or molecules
To calculate energy of electromagnetic radiation
E = hf = hc/wavelength
Rydberg constant
R = 2.18 x 10^(-18) J
Or
R = 1.097 x 10^7 m^-1
Calculate energy of the emitted/ absorbed photon when electron is moved between energy level n
Delta E = (Rydberg constant) x (1/n_final^2 - 1/n_initial^2)
Delta E < 0 : E is released, electron moves from higher to lower energy level
Delta E > 0 : E is absorbed, electron moves from lower to a higher energy level
Michaelis-Menten equation
Enzyme kinetics
How reaction rate (v) changes when substrate concentration [S] changes
Lineweaver - Burk plots
Enzyme kinetics
Double-reciprocal transformation of Michaelis-Menten plot
Oxidation
Loss of electrons
Increased oxidation state
More C-O/ C-N bonds
Less C-H bonds
Reduction
Gain electrons
Decreased oxidation state
Less C-O / C-N bonds
More C-H bonds
OIL RIG
Oxidation is Loss of electrons
Reduction is Gain of electrons
Reduction of alkene
Hydrogenation of alkene. This is reduction because new C-H bonds are formed.
Oxidation of alkene
New C-O bonds are formed
Calculate the heat q at phase change
Unit: J, kJ, cal
Calculate heat q between phase change (related to temperature change!)
Unit: J, kJ, cal
Volume of 1 mole of any gas at STP (T = O celcius, p = 1 atm)
1 mol = 22.4 L
Avogadro’s law
V1/ n1 = V2/ n2
Assume T and p are constant.
V and n are directly proportional to each other.
Kinetic molecular theory (Ideal Gases)
- Gas particles are in continuous, random motion
- Avg kinetic energy of gas particles is directly proportional to temperature; all gas particles will have the same kinetic energy at a given T.
Avg KE = (3/2)kT - (*) Gas particles have no volume (negligible volume compared to their container)
- (*) Gas particles do not interact with each other (no attraction/ repulsion). Pressure of gas comes from collision btw gas particles and wall of container.
- All gas particle collisions are elastic; the overall kinetic energy is conserved.
Conditions favor ideal gas behavior
High T
Low pressure
Large volume
Any conditions favoring the formation of liquid make the gas deviate from ideal behavior.
Molecules with polar bonds exert more attractive force with each other -> less likely to behave like ideal gas.
Boyle’s Law
Volume and pressure of a gas are inversely proportional at constant T.
P1V1 = P2V2
Charles’s law
V1 / T1 = V2 / T2
Volume and temperature of a gas are directly proportional under constant pressure and mole of gas.
Gay-Lussac’s Law
P1 / T1 = P2 / T2
Assume constant volume and number of moles, pressure of gas is proportional to its temperature.
Ideal Gas Law
PV = nRT
R = 0.08 L.atm/K.mol
or
R = 8.314 J / K.mol
Van der Waals equation (for real gas)
Compare pressure of real gas vs. ideal gas under STP (T = 273K or OoC; p = 1 atm)
Under STP, real gas has a smaller pressure compared to an ideal gas.
Compare pressure of real gas vs. ideal gas at extreme pressure (container of small V)
Real gas has higher pressure than ideal gas because size of gas particle (b value) is no longer negligible. When the V of container is too small, the gas particles press against the wall more often, and the bigger particles increase pressure against the wall.
Compare pressure of real vs. ideal gas at low T.
Real gas has lower pressure compared to ideal gas at low T.
Dalton’s Law
The total pressure of a mixture of gases equals the sum of the partial pressure of its components.
Graham’s Law of diffusion (gases)
When a gas is effusing (escaping from a small opening), the smaller, lighter particles escape faster.
IR peak values for some types of bonds
Calculate the number of stereoisomers
2^n
n = the number of chiral centers
What is a chiral center?
Chiral center is a tetrahedral atom with 4 different groups / substituents bonded to the atom so that the compound cannot be superimposed on its own mirror image.
VSEPR theory
Relation btw Km and affinity of enzyme
Km is the concentration of substrate at which point the enzyme achieves half Vmax.
Higher Km value indicates that enzyme has lower affinity for its substrate because it requires a greater substrate concentration to achieve Vmax.
T/F
Phase changes from solid -> liquid -> gas are endothermic reactions.
True
Because gas contains more heat energy than liquid, and liquid contains more heat E than solid.
T/ F
Phase changes from gas to liquid to solid are endothermic.
False.
Gas -> Liquid -> Solid are exothermic (release heat).
Some common strong acids and bases
Effective nuclear charge (Zeff)
The actual attractive force of the positively-charged nucleus on the atom’s valence electrons.
Symbol of atom (atomic number Z and atomic mass A)
T/F
There is increase in the avg kinetic energy, so there is an increase in entropy (S)
True
T/F
Electrons in orbitals that are more spatially compact are held more tightly to the positively charged nucleus. Therefore, the ionization energy is predicted to be higher.
True
Relationship btw delta(G) and reduction potential Ecell
Is alcohol more polar than aldehyde/ ketone?
Yes, alcohol is more polar than aldehyde and ketone due to its ability to donatebhydrogen bond.
Is silica gel polar or nonpolar?
Silica gel is polar
Coordinate covalent bond
A covalent bond in which both electrons come from the same atom.
Ex: Lewis acid w/ Lewis base
Metal cation w/ an electron pair donor
How to determine the relative thermodynamic stability of isomers?
Based in the amount of heat produced when the compound is combusted.
Less heat, greater stability
