Playbook
Chemical Kinetics
125 q - 3.00/paper - 2% HARD. Three pages, 103 questions, no HARD: rates, rate laws and first-order half-life.
- Questions in the bank
- 125
- q/paper (2024–25 papers)
- 3.00
- Tagged HARD
- 2%
- Subtopics
- 6
Strand: Calculate
When you’ll see it
A rate, a rate law, an order, a percent decomposed in a time, a half-life, or a temperature change and an activation energy.
How this chapter is tested
125 q at exactly 3.00 a paper, 2% HARD. 103 of the 125 questions sit on three pages that have never produced a HARD question: rate and stoichiometry (25 q), rate law and order (36 q), and first-order kinetics (42 q).
The first-order page is the paper's favourite: k = (2.303/t) log(a/(a − x)) from a percent decomposed, and t½ = 0.693/k in either direction. With no calculator, the logs you need are the three to memorise — log 2 = 0.301, log 3 = 0.477, log 5 = 0.699. The HARD sits on the small Arrhenius page (8 q, 38%).
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Rate and stoichiometry
For aA → bB: rate = −(1/a)d[A]/dt = (1/b)d[B]/dt. Divide by the coefficient.
Order from a rate law or data
Order is experimental: the sum of the exponents. Doubling a concentration of order n multiplies the rate by 2ⁿ.
First and zero order
First: k = (2.303/t) log(a/(a − x)), t½ = 0.693/k (independent of a). Zero: t½ = a/(2k).
Arrhenius
log(k₂/k₁) = (Eₐ/2.303R)(1/T₁ − 1/T₂).
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Missing the coefficient in a rate
In N₂ + 3H₂ → 2NH₃, NH₃ forms at twice the rate N₂ is used. The 1:1 answer is always an option.
Order equals molecularity
Molecularity is for an elementary step and is a whole number; order is measured and can be fractional or zero. H₂ + Br₂ has order 3/2.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Chemical Kinetics notesDrill every chemical kinetics question
125 questions from the bank, scoped to 6 bundled subtopics.
Drill one subtopic at a time
The 6 subtopics this playbook covers, in catalog order.
- Rate of Reaction, Stoichiometry and Average RateDrill
- Rate Law, Order, Molecularity and Rate ExpressionDrill
- First-Order Kinetics, Rate Constant and Half-LifeDrill
- Zero-Order KineticsDrill
- Reaction Mechanism, Intermediates and Rate-Determining StepDrill
- Temperature Dependence, Arrhenius and Collision TheoryDrill
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