Rate Law Expression

$\text{rate} = k[A]^m[B]^n$

• $k$ = rate constant (specific rate constant)
• $m$ = order with respect to A
• $n$ = order with respect to B
• $m + n$ = overall order of reaction

Critical Points About Order

1. Determined experimentally (not from balanced equation)
2. Can be: 0, positive integer, negative integer, or fraction
3. Applies to both overall and elementary reactions
4. Can change with conditions (temperature, concentration range)

Critical Points About k

1. Temperature-dependent (increases with T)
2. Independent of concentration
3. Unique for each reaction at a given temperature
4. Units depend on overall order

Method of Initial Rates

To find order experimentally:

• Keep [B] constant, vary [A] → measure rate changes to find m
• Keep [A] constant, vary [B] → measure rate changes to find n

$m = \frac{\log(\text{rate}_2/\text{rate}_1)}{\log([A]_2/[A]_1)}$

Important Examples