5.2 Introduction to Rate Law

01Rate = k[A]^m[B]^n

Orders (m, n) come from experiment, never from coefficients (unless the step is elementary). Compare trials where only one concentration changes.

Overall order = m + n. Units of k change with overall order.

Double [A]: rate ×1 → 0th, ×2 → 1st, ×4 → 2nd.

Worked example: Doubling [A] (with [B] fixed) quadruples rate; doubling [B] doesn't change it → rate = k[A]².

Key takeaways

Watch outDon't read orders off the balanced equation.

Quick check

1.Tripling [A] triples rate. Order in A?

2.Rate = k[A][B]². Overall order?

3.Units of k for a first-order reaction?