Mcat General Chemistry

Front 1

Alpha Decay

Back 1

N = -2
z = - 2
A = -4

Front 2

B - Decay

Back 2

N = -1
Z = +1
A =

Front 3

B + Decay

Back 3

N = +1
Z = -1
A =

Front 4

Emission Spectrum

Back 4

(Low) Radio Micro IR Visible UV X-Ray Gamma Rays (High)

Front 5

Formal Charge

Back 5

FC = #V - #B - #L

V = Valence
B = Bonds
L = Lone Pairs

Front 6

Linear

Back 6

sp

Front 7

Trigonal Planar

Back 7

sp2

Front 8

Tetrahedral

Back 8

sp3

Front 9

Trigonal bypyramidal

Back 9

sp3d

Front 10

Octehedral

Back 10

sp3d2

Front 11

Intermolecular bonding

Back 11

Relatively weak interactions between neutral molecules
Van der waals forces encompass all
Dipole-dipole interactions
London dispersion forces are instantaneous dipole-dipole interactions between neighboring molecules
Very week
Can be stronger in larger chains of carbon or sulfur
Hydrogen bonding:
Strongest type of intermolecular force
Occurs only between H-N, H-O, or H-F molecules

Front 12

Vaporization

Back 12

Liquid to Gas

Front 13

Condensation

Back 13

Gas to Liquid

Front 14

Sublimation

Back 14

Solid to Gas

Front 15

Deposition

Back 15

Gas to Solid

Front 16

Fusion

Back 16

Solid to liquid

Front 17

Crystallization

Back 17

Liquid to Solid

Front 18

Triple Point

Back 18

All 3 phases exist in equilibrium on a phase change graph

Front 19

Critical Point

Back 19

point above which there is no distinction between gas and liquid in a phase change graph.

Front 20

Atmospheric Pressure

Back 20

1 atm=101 kPa= 760 torr=760 mm Hg

Front 21

Ideal Gases

Back 21

Follows the kinetic-molecular theory:
Molecules insignificant to volume gas
Molecules move in strait lines
No Intermolecular Forces
KEave ~ T
Most gases act Ideal

Front 22

Ideal Gas Law

Back 22

Ideal Gas Law
PV=nRT
P=pressure of gas
V=volume of container in L
n=# moles of gas
R=universal gas constant: .0821 Latm/molK
T=absolute temp of gas (in Kelvin)
Combined gas Law:
P1V1/T1=P2V2/T2
1 mol of gas at STP has a volume of 22.4 L

Front 23

Dissolution

Back 23

Process of dissolving

Front 24

Solute

Back 24

Less present material in solution

Front 25

Solvent

Back 25

Most present material in solution

Front 26

Saturated Solution

Back 26

Rate of dissolution = rate of precipitation

Front 27

Molarity

Back 27

Moles of solute/Liters of solution

Front 28

Molality

Back 28

Moles of solute/Kg of solvent

Front 29

Normality

Back 29

Measure number of ions of most abundant ion in solution

Front 30

Mole Fraction

Back 30

Number of moles of product/ number of moles in solution

Front 31

Salt Solubility Rules

Back 31

All Group I (Li+, Na+, K+…) & ammonium (NH4+) salts are soluble
All NO3-, ClO4- & C2H3O2- salts are soluble
All Ag+, Pb2+/Pb4+ & Hg22+/Hg2+ salts are insoluble, except for those above

Front 32

Phase Solubility Rules

Back 32

Temp ↑ means solubility solids in liquids ↑
Temp ↑ means solubility gasses in liquids ↓
Pressure ↑ solubility gasses ↑

Front 33

Kinetics

Back 33

The study of how & how fast reactions take place
Says nothing about their spontaneity
Considers the intermediate steps of a reactions
Rate determining step (slowest step) determines overall rate

Front 34

Reaction Rate

Back 34

Indicates how fast the reactants are being consumed, or how quickly the products are being formed.
Determined by:
How frequently molecules collide
Their orientation
Their energy
The activation energy

Front 35

Equilibrium

Back 35

Most reactions are reversible and eventually reach a dynamic equilibrium
Equilibrium constant (Keq) is specific to a reaction at a temperature.
If we have: aA + bB  cC + dD Then Keq = ([C]^c[D]^d)/([A]^a[B]^b)
Ignore Solids and pure liquids and slvnts in dilute sltns
Partial Pressures of gasses can be used
Gives favored direction
Keq > 1 => favors products
Keq < 1 => favors reactants

Front 36

Le Châtelier’s Principle

Back 36

A system at equilibrium will try by neutralizing any imposed change(aka stress)
CO + 2 H2 + Heat ⇌ CH3OH
If we add CH3OH? Rxn ← untill equilibrium is reached
If we remove CH3OH? Rxn 
Add Hydrogen? Rxn 
Remove CO? Rxn 
Shrink the container?
From PV=nRT we know that if V ↓ then P ↑ and fewer moles of substance will be favored
Rxn 
Add heat? Rxn 
Adding a catalyst
The catalyst increases the rate of foreword and reverse reactions equally, so Keq is unaffected

Front 37

Solubility Product Constant (Ksp)

Back 37

Solubility Product constant (Ksp)
Gives the extent to which a substance dissolves
CaF2 (s)  Ca2+ (aq) + 2F- (aq)
Ksp=[Ca2+][F-]^2

Front 38

The Common Ion Effect

Back 38

The more soluble ion (greater Ksp) will cause a less soluble ion (lower Ksp) to fall out of solution

Front 39

Arrheinus

Back 39

Acids give H+ (H3O+) in water
Bases give OH- in water

Front 40

Bronsted-Lowry

Back 40

Acids are proton (H+) donors
Bases are proton (H+) acceptors
Most common type on MCAT

Front 41

Lewis

Back 41

Rarely used
Acids are e- pair acceptors
Bases are e- pair donors

Front 42

Strong Acids

Back 42

HI
HBr
HCl
HClO4
H2SO4
HNO3
If not above, acid is weak

Front 43

Strong Bases

Back 43

Group I OH and O
Larger Group II OH and O
NaNH2

Front 44

Weak Acid equation

Back 44

Ka = [H3O+][A-]/[HA]
Calculated same as Keq
Ka (acid ionization) constant:
>1 means strong—products favored
<1 means weak—reactants favored

Front 45

Weak Base equation

Back 45

B + H2O  HB+ + OH-
Kb=[HB+][OH-]/[B]
Big Kb= strong base
Little Kb= weak base
Kb=base ionization

Front 46

Kw

Back 46

Autionization (or self-ionization) of water
H2O + H2O  H3O+ + OH-
Kw = [H30+][OH-]
Kw at 25°C = 1.0 x 10-14
Conc. of H3O, OH same:
Kw= x*x = 1.0 x 10^-14=x^2
x =10^-7

Front 47

Conjugates

Back 47

The one with the extra H is the acid, the one without it the base
The conjugate base of a strong acid or the conjugate acid of a strong base have no properties on water
The conjugate base off a weak acid is a weak base and the conjugate acid of a weak base is a weak acid
For Conjugate Ka*Kb=Kw
so pKa + pKb = 14

Front 48

P something general

Back 48

pX= -logX
pKa= -log Ka
so if Ka = 3 x 10^-6
pKa = between 56
pKb works the same
pH works the same with [H3O+]
pOH works the same with [OH-]
Because [H3O+] netural H2O = 10^-7
pH = 7 for neutral
pH <7 means acid
pH >7 means basic
The lower pH or pKa the more acid, the lower the pOH or pKb the more basic
For a solution [H3O+][OH-]=Kw
pOH + pH = 14

Front 49

Neutrilization Reaction

Back 49

Acid + Base  Salt + Water
All neutralization reactions release heat
If salt produced is neutral, then pH is neutral
Strong or Weak doesn’t matter
For complete neutralization
a x [A] x Va = b x [B] x Vb
a= acidic H+ per unit, b = # H+ that can be accepted
V=volume

Front 50

Buffers

Back 50

A solution that resists changes in pH when relatively small amount of acid or base is added.
Comes from weak acid and conjugate base (or vice versa) in about equal concentrations
Henderson-Hasselbalch equation:
pH = pKa –log [weak acid]/[conjugate base]
pH = pKa – log [HA]/[A-]
So pKa should be very close to desired pH

Front 51

Equivalance point

Back 51

where the weak acid (or base) has been completely neutralized

Front 52

First Law of Thermodynamics

Back 52

The total energy of the universe is constant
Energy cannot be created or destroyed, only converted from one form to another

Front 53

Second Law of Thermodynamics

Back 53

Changes tend to lean towards creating greater disorder.
i.e. a change that proceeds spontaneously in one direction will not proceed spontaneously in the reverse.

Front 54

Physical Thermodynamics

Back 54

ΔE = q + w
q= heat
w= work
+w is on the system
-w is by the system
Expanding gases cool
Compressing gases warm

Front 55

Isobaric

Back 55

Constant Pressure

Front 56

Isochoric

Back 56

Constant Volume

Front 57

Isothermal

Back 57

Constant Temperature

Front 58

Adiabatic

Back 58

Done without heat exchange

Front 59

Entropy Definition

Back 59

Nature favors disorder, the second law of thermodynamics
Rxns can occur in which entropy decreases, but it will require an input of energy or a net gain of energy by created more stable bonds
ΔS=Sproducts-Sreactants
Some guidelines for Entropy:
Liquids > Solids
Gases > Liquids
Particles in sltn > undissolved solids
More molecules > Fewer molecules
ΔSreverse=- ΔSforward

Front 60

Enthalpy Definition

Back 60

Measures Heat Energy given off or absorbed when bonds are broken or formed when rxn run at constant pressure
A bond is more stable than not having a bond:
When a bond is formed, energy is released
A bond must be broken by energy input
ΔH=Hproducts-Hreactants
Heat of Formation (ΔHf)
the amount of energy required to make one mole of compound from pure elements in their natural state
Standard state conditions are used to determine ΔH
25°C at 1 atm
symbolized as ΔH°
Don’t confuse this with STP!

Front 61

Heat Summation

Back 61

If a reaction has multiple steps, the sum of the energies absorbed and given off of the individual steps equals that of the overall reaction.
It doesn’t matter how you get from point a to point be, the overall change in energy will always be the same.
2 rules:
If the reaction is reversed, reverse the sign of ΔH.
If the reaction is multiplied by a constant, multiply ΔH by a constant

Front 62

Gibbs Free Energy

Back 62

The energy available (free) to do useful work from a chemical reaction
ΔG < 0 => spontaneous
ΔG = 0 => at equilibrium
ΔG > 0 => non-spontaneous
ΔG  = - ΔG of 
ΔG=ΔH-TΔS

Front 63

Kinetics vs Thermodynamics

Back 63

Remember that Kinetics and Thermodynamics are different.
The MCAT will try and get you to confuse them—don’t let them.
Thermodynamics predicts whether or not a reaction will occur. Kinetics predicts how quickly that reaction will occur.
Diamondgraphite is spontaneous, but very very slow.

Front 64

Redox

Back 64

Oxidation state= # e- donated or accepted in a bond by an atom
When the oxidation state changes, the reaction is called a redox reaction
Oxidation:
Oxidation # ↑
Loose e-
Reduction
Oxidation # ↓
Gain e-
LEO Goes GER
OIL RIG
Oxidized atom is a reducing agent
Reduced atom is an oxidizing agent

Front 65

Galvanic Cell

Back 65

Oxidation occurs at the anode
Reduction at the cathode
Vowels with vowels, consonants with consonants
Red Cats of America
Anode and Cathode generally are the metal which is being oxidized or reduced
How would the Line notation of the one above look?
Pt(s)| Fe2+, Fe3+ || H+, MnO4-, Mn2+ |Pt(s)
More generally:
Anode|sltn at anode||sltn at cathode|Cathode

Front 66

Reduction Potential

Back 66

Determined by seeing what would happen if cell were run with the standard reference electrode
2H+ + 2e-  H2
Defined as 0 V
Given as standard reduction potentials
Reverse to get oxidation potentials
Positive voltage = spontaneous
ΔG=-nFE
n=# electrons transferred
F = Faraday (~96,500 C)
E=cell voltage
This is why a positive voltage is spontaneous—it gives a - ΔG