Simulate first, second, and zero-order reaction kinetics.
Reaction kinetics is the study of how fast chemical reactions proceed and what factors control that rate. For AP Chemistry Unit 5 and the USNCO examination, kinetics questions require both conceptual understanding (why rates change) and quantitative fluency (rate laws, half-life, and the Arrhenius equation).
The rate law for a reaction is determined experimentally, not from the balanced equation. For the reaction A + B → products, the rate may follow rate = k[A]^m[B]^n, where m and n are the reaction orders with respect to A and B respectively. These exponents must be measured from experimental data — they have no required relationship to stoichiometric coefficients.
Integrated rate laws connect concentration to time. For a first-order reaction: ln[A] = ln[A]₀ − kt, giving a straight line when ln[A] is plotted against time. For second order: 1/[A] = 1/[A]₀ + kt, linear in 1/[A] vs. time. For zero order: [A] = [A]₀ − kt, linear in [A] vs. time. Identifying reaction order from a graph is a standard AP MCQ question — whichever plot is linear reveals the order.
The half-life of a reaction is the time for the concentration to fall to exactly half its initial value. For first order reactions, t₁/₂ = ln2/k = 0.693/k — independent of initial concentration. This is why radioactive decay (always first order) has a constant half-life. For second order reactions, t₁/₂ = 1/(k[A]₀), which depends on the starting concentration.
The Arrhenius equation links the rate constant to temperature: k = Ae^(-Ea/RT). Taking the logarithm: ln k = ln A − Ea/RT. A plot of ln k versus 1/T is linear with slope −Ea/R, allowing activation energy to be determined experimentally. This relationship explains why reaction rates roughly double for every 10°C temperature increase near room temperature.
Use this kinetics simulator to explore rate laws, plot concentration–time graphs for all three orders, and apply the Arrhenius equation to understand how temperature and activation energy govern chemical reaction rates.