Reaction Kinetics — A/L Chemistry

What must I remember about Reaction Kinetics?

• Reaction rate measures the change in concentration of a reactant or product per unit time: Rate = -d[Reactant]/dt = +d[Product]/dt.
• Rate equation: Rate = k[A]^m [B]ⁿ, where k is the rate constant, and exponents m and n are reaction orders with respect to reactants A and B.
• Reaction order can only be determined experimentally and cannot be deduced from the stoichiometric coefficients of the overall balanced equation.
• Collision theory requirements: reacting particles must collide with sufficient kinetic energy (E ≥ Ea, activation energy) and appropriate spatial orientation.
• In multi-step mechanisms, the overall rate law matches the molecularity and stoichiometry of the slowest step, called the rate-determining step.

Test yourself (1 minute)

1. Units of rate constant k

   (mol dm⁻³)¹⁻ⁿ s⁻¹ (where n is the overall reaction order).

2. Arrhenius equation

   k = A e^-Ea/RT or ln(k) = ln(A) - Ea/(RT). The slope of a plot of ln(k) against 1/T is -Ea/R.

3. Why does a 10 °C temperature rise roughly double a reaction rate?

   A temperature rise of 10 °C roughly doubles the reaction rate because of the exponential increase in the fraction of molecules with E ≥ Ea.

Practise Reaction Kinetics questions today

Source: NIE G.C.E. (A/L) Chemistry Syllabus (Unit 11)

What comes next?

Next in the syllabus

Where does Reaction Kinetics fit in the syllabus?

Grade 13 · Term 1