Cracking the SAT Chemistry Subject Test

FORMULA CHEAT SHEET

• density =

Heat

q = mcΔT

q = Heat

m = mass

c = specific heat

ΔT = Temperature change

Spontaneity

• ΔG = ΔHTΔS

ΔG < 0 means that a reaction is spontaneous at this temperature

• ΔT = kmi

Freezing Point Depression
& Boiling Point Depression

i: whole number equaling the number of particles a substance dissolves into

k: solvent constant

m: molality (NOT molarity)

molarity =

molality =

mole fraction =

Ideal Gas Law

PV = nRT

P = pressure in atm (or mmHg or torr)

V = volume in liters

n = number of moles of gas particles in the container

R = the ideal gas constant

T = temperature in Kelvin

To calculate the ideal gas constant, use the following formula:

R = .08

Conversions

• Pressure:

1 ATM = 760 torr = 760 mmHg

• Energy (Heat):

1 Calorie = 1000 calories = 4000 joules

• Temperature:

0°C = 273 Kelvin

25°C = 298 K

Facts to Know

• To find the mass of a mole of a substance, multiply the formula weight by the number of moles.

• 1 mol of gas at STP occupies 22.4 L of volume.

Solubility

• All alkali and ammonium (NH4+) compounds are soluble. The alkali metals are included in group IA (Li+, NA+, K+, Rb+, Cs+).

• All acetates (CH3COO), chlorates (), nitrates (), and perchlorates () are soluble.

• Pbn+, Hgn+, and Agn+ salts are insoluble, unless they are paired with one of the anions from the previous rule.

Oxidation Rules

1. When oxygen is in a compound, its oxidation state is usually –2 (it has been reduced). One important exception is oxygen in a peroxide such as hydrogen peroxide (H2O2). In a peroxide, oxygen has an oxidation state of –1.

2. When an alkali metal (Li, Na, etc.) is involved in a compound, its oxidation state is always +1 (it's been oxidized).

3. When an alkaline earth metal (Be, Mg, etc.) is involved in a compound, its oxidation state is +2.

4. When a halogen (F, Cl, etc.) is involved in a compound, its oxidation state is often –1. The oxidation state of fluorine in a compound is always –1.

5. When hydrogen is combined with a nonmetal, its oxidation state is +1. When hydrogen is combined with a metal, its oxidation state is –1.

6. In any compound, the sum of all oxidation states is zero.

Constants

• Avogadro's number: 6 × 1023 molecules/mole

Prefixes

Prefixes for Organics

Meth - 1

Eth - 2

Prop - 3

But - 4

Pent - 5

Hex - 6

Hep - 7

Oct - 8

Non - 9

Dec - 10

Prefixes for Scientific Notation

nano n 10-9

micro  10-6

milli m 10-3

centi c 10-2

kilo k 10-3

mega M 106

Electrochemistry

OIL

Oxidation Is Losing Electrons

RIG

Reduction Is Gaining Electrons

AN OX

Oxidation Occurs at Anode

RED CAT

Reduction Occurs at Cathode

• Galvanic Cell: E°cell > 0 means reaction is spontaneous and energy is released (battery).

• Electrolytic Cell: E°cell < 0 means the reaction is NOT spontaneous and requires a voltage source (electro plating).

Equilibrium

Periodic Trends

Acid-Base

pH = pKa + log

pH = –log10[H+]

pH > 7: Basic

pH = 7: Neutral

pH < 7: Acidic

Strong Acids:

HCI, HI, H2SO4, HBr, HClO4, HNO3

Strong Bases:

All Group I Hydroxides