#1 Free Reaction Rate Calculator / Chemical Kinetics Calculator 2025

Chemical kinetics is the branch of chemistry concerned with understanding the rates of chemical reactions. It explores how different experimental conditions can influence the speed of a reaction and yields information about the reaction's mechanism and transition states.

Reaction Rate:

The reaction rate (or speed) is the change in concentration of a reactant or product per unit of time. For a general reaction, the rate can be expressed by a rate law.

Rate Law:

A rate law is an equation that links the reaction rate with the concentrations of reactants and a rate constant. For a general reaction: aA + bB → cC + dD, the rate law is often of the form:

Rate = k[A]^m[B]ⁿ

Where:

• Rate: The reaction rate (units depend on concentration and time, e.g., M/s, mol L^-1s^-1).
• k: The rate constant. Its value is specific to a reaction at a particular temperature. Its units depend on the overall order of the reaction.
• [A], [B]: Molar concentrations of reactants A and B.
• m, n: The orders of the reaction with respect to reactants A and B, respectively. These are usually small integers (0, 1, 2) or sometimes half-integers, and they must be determined experimentally. They are not necessarily equal to the stoichiometric coefficients (a, b).

Order of Reaction:

• Order with respect to a reactant (m or n): Indicates how the rate is affected by the concentration of that particular reactant.
  • If m=0 (zero-order with respect to A), Rate is independent of [A].
  • If m=1 (first-order with respect to A), Rate is directly proportional to [A].
  • If m=2 (second-order with respect to A), Rate is proportional to [A]².
• Overall Order of Reaction: The sum of the individual orders (m + n + ...). This determines the units of the rate constant k.
  • Overall 0^th order: units of k = M·time^-1
  • Overall 1^st order: units of k = time^-1
  • Overall 2^nd order: units of k = M^-1·time^-1
  • Overall 3^rd order: units of k = M^-2·time^-1

Note: This calculator uses the form Rate = k[A]^m[B]ⁿ. For reactions involving a single reactant (e.g., A → Products), you can set [B] = 1 and n = 0 in the calculator.

1. Enter the Rate Constant (k). This value must be positive. Be mindful of its units, as they depend on the overall reaction order.
2. Enter the Concentration of Reactant A ([A]). This must be a non-negative number. Ensure unit consistency with k.
3. Enter the Order of Reaction with respect to A (m). This is typically a small non-negative integer (e.g., 0, 1, 2) or half-integer.
4. Enter the Concentration of Reactant B ([B]). This must be a non-negative number. (If reactant B is not involved or for a single-reactant rate law, you can set [B] = 1 and n = 0).
5. Enter the Order of Reaction with respect to B (n). Similar to m. (Set n = 0 if B is not part of the rate-determining step or for a single-reactant rate law where A is the only reactant considered).
6. Click the "Calculate Reaction Rate" button.
7. The calculated Reaction Rate and a step-by-step solution will be displayed below.
8. An interactive graph will show how the rate changes with the concentration of reactant A (keeping other parameters constant).
9. Ensure all units are consistent (e.g., if [A] is in Molarity (M) and time in seconds (s), then k must have units compatible for the rate to be in M/s).