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Ideal Gas Law

PV = nRT

Relates pressure, volume, moles and temperature of a gas.

Molarity

M = \frac{n}{V}

Concentration in moles of solute per litre of solution.

Moles from Mass

n = \frac{m}{M}

Number of moles from mass and molar mass.

pH

pH = -\log_{10}[H^+]

Acidity from hydrogen-ion concentration.

pOH

pOH = -\log_{10}[OH^-]

Basicity from hydroxide-ion concentration.

Henderson–Hasselbalch

pH = pK_a + \log\frac{[A^-]}{[HA]}

pH of a buffer solution.

Dilution Equation

C_1 V_1 = C_2 V_2

Relates concentration and volume before and after dilution.

Rate Law

r = k[A]^m[B]^n

Reaction rate as a function of reactant concentrations.

Arrhenius Equation

k = A e^{-E_a/RT}

Temperature dependence of the reaction rate constant.

Gibbs Free Energy

\Delta G = \Delta H - T\Delta S

Predicts spontaneity of a reaction.

Nernst Equation

E = E^\circ - \frac{RT}{nF}\ln Q

Cell potential under non-standard conditions.

Beer–Lambert Law

A = \varepsilon l c

Absorbance of light by a solution.

Equilibrium Constant

K = \frac{[C]^c[D]^d}{[A]^a[B]^b}

Ratio of product to reactant concentrations at equilibrium.

Combined Gas Law

\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}

Relates two states of a fixed amount of gas.

Percent Yield

\% = \frac{\text{actual}}{\text{theoretical}} \times 100

Efficiency of a chemical reaction.

Avogadro's Number

N = n \times N_A

Number of particles from moles.

Density

\rho = \frac{m}{V}

Mass per unit volume of a substance.

Percent Composition

\% = \frac{\text{mass of element}}{\text{molar mass}} \times 100

Mass percentage of an element in a compound.

Boyle's Law

P_1 V_1 = P_2 V_2

Pressure and volume are inversely related at constant temperature.

Charles's Law

\frac{V_1}{T_1} = \frac{V_2}{T_2}

Volume is proportional to temperature at constant pressure.

Ideal Gas Law

PV = nRT

Relates pressure, volume, moles, and temperature of a gas.

Boyle Law

P_1 V_1 = P_2 V_2

At constant temperature, pressure and volume are inversely related.

Charles Law

\frac{V_1}{T_1} = \frac{V_2}{T_2}

At constant pressure, volume is proportional to temperature.

Gay-Lussac Law

\frac{P_1}{T_1} = \frac{P_2}{T_2}

At constant volume, pressure is proportional to temperature.

Avogadro Number

N_A = 6.022\times 10^{23}

Number of particles in one mole.

Number of Particles

N = n\times N_A

Particles from moles and Avogadro number.

Gas Density

\rho = \frac{PM}{RT}

Density of an ideal gas.

Rate Law

rate = k[A]^m[B]^n

Reaction rate as a function of reactant concentrations.

First-Order Half-Life

t_{1/2} = \frac{0.693}{k}

Half-life of a first-order reaction.

Mass Percent

\% = \frac{m_{solute}}{m_{solution}}\times 100

Concentration as a percentage by mass.

Molality

b = \frac{n_{solute}}{m_{solvent}}

Moles of solute per kilogram of solvent.

Combined Gas Law

\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}

Combines Boyle, Charles, and Gay-Lussac laws.

Enthalpy Change

\Delta H = H_{products} - H_{reactants}

Heat absorbed or released at constant pressure.

Hess Law

\Delta H = \sum \Delta H_{steps}

Total enthalpy change is the sum of step changes.

pH and pOH

pH + pOH = 14

Relationship between acidity and basicity at 25°C.