Rate of Reaction Calculator
Calculate reaction rate using the rate law r = k[A]ⁿ, from concentration changes, or by integrated rate laws. Includes half-life for 0th, 1st, and 2nd order reactions.
mol/L
Reaction Rate r (mol/(L·s))
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Half-Life t½ —
Units of k —
Extended More scenarios, charts & detailed breakdown ▾
mol/L
Rate r (mol/(L·s))
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Professional Full parameters & maximum detail ▾
mol/L
s
Initial Rate r₀ (mol/(L·s))
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Half-Life t½ (s) —
[A] at time t (mol/L) —
% Reactant Remaining —
Units of k —
Linear Plot for Order ID —
How to Use This Calculator
- Select the reaction order (0, 1, or 2).
- Enter the rate constant k and concentration [A].
- Read the instantaneous rate. Use tabs for concentration change method or half-life calculations.
Formula
r = k[A]ⁿ (rate law)
t½ = 0.693/k (1st order) | t½ = 1/(k[A]₀) (2nd order)
Example
Example (1st order): k = 0.05 s⁻¹, [A] = 0.2 mol/L. r = 0.05 × 0.2 = 0.01 mol/(L·s). t½ = 0.693/0.05 = 13.86 s.
Frequently Asked Questions
- The rate law relates reaction rate to concentration: r = k[A]ⁿ[B]ᵐ. The order n is determined experimentally, not from stoichiometry. k is the rate constant (units depend on order).
- Plot concentration data: if [A] vs t is linear → 0th order; if ln[A] vs t is linear → 1st order; if 1/[A] vs t is linear → 2nd order. The straight-line plot identifies the order.
- Units depend on order: 0th order: mol/(L·s); 1st order: 1/s; 2nd order: L/(mol·s). General formula: k units = (mol/L)^(1−n)/s.
- 1st order: t½ = ln(2)/k = 0.693/k (independent of concentration). 2nd order: t½ = 1/(k[A]₀) (depends on initial concentration). 0th order: t½ = [A]₀/(2k).
- k = A·exp(−Ea/RT), where Ea is activation energy, A is the pre-exponential factor, R = 8.314 J/(mol·K), and T is temperature in Kelvin. Higher temperature always increases k.
Related Calculators
Sources & References (5) ▾
- Chemical Kinetics — ACS Education — American Chemical Society
- OpenStax Chemistry 2e, Chapter 12 — Kinetics — OpenStax
- IUPAC Compendium of Chemical Terminology — Rate of Reaction — IUPAC
- Atkins, P. & de Paula, J. — Physical Chemistry, 10th Ed., Ch. 17 — Chemical Kinetics — Oxford University Press
- LibreTexts Chemistry — Integrated Rate Laws — LibreTexts