Examples: Radioactive decay, hydrogenation of ethene.

Equation: $k = Ae^{-E_a/RT}$
- $k$: rate constant
- $A$: Arrhenius factor (or frequency factor)
- $E_a$: activation energy (J mol$^{-1}$)
- $R$: gas constant
- $T$: temperature (K)
Logarithmic Form: $\ln k = -\frac{E_a}{RT} + \ln A$
Two Temperatures: $\ln \frac{k_2}{k_1} = \frac{E_a}{R} \left( \frac{1}{T_1} - \frac{1}{T_2} \right)$ or $\log \frac{k_2}{k_1} = \frac{E_a}{2.303R} \left( \frac{T_2 - T_1}{T_1 T_2} \right)$
Increasing temperature or decreasing $E_a$ increases reaction rate.

Reactant molecules are assumed to be hard spheres that must collide to react.
Collision Frequency ($Z$): Number of collisions per unit volume per second.
Effective Collisions: Collisions with sufficient kinetic energy (threshold energy) AND proper orientation.
Rate Equation: Rate $= P Z_{AB} e^{-E_a/RT}$
- $P$: probability (steric) factor, accounts for proper orientation.
- $Z_{AB}$: collision frequency for reactants A and B.

Definition: Homogeneous mixture of two or more components.
Components:
- Solvent: Component in largest quantity, determines physical state.
- Solute: Other components.
Binary Solutions: Contain two components.

Type	Solute	Solvent	Example
Gaseous	Gas	Gas	Air ($\text{O}_2 + \text{N}_2$)
	Liquid	Gas	Chloroform in $\text{N}_2$
	Solid	Gas	Camphor in $\text{N}_2$
Liquid	Gas	Liquid	$\text{O}_2$ in water
	Liquid	Liquid	Ethanol in water
	Solid	Liquid	Glucose in water
Solid	Gas	Solid	$\text{H}_2$ in Palladium
	Liquid	Solid	Amalgam of Mercury with Sodium
	Solid	Solid	Copper in Gold

Mass Percentage (w/w): $\frac{\text{Mass of component}}{\text{Total mass of solution}} \times 100$
Volume Percentage (V/V): $\frac{\text{Volume of component}}{\text{Total volume of solution}} \times 100$
Mass by Volume Percentag