Calculate rate constants from reaction rate, concentrations, reaction orders, integrated rate laws, or Arrhenius temperature and activation energy data.

Rate = k[A]^m[B]^n. Orders are experimental inputs; k units depend on m + n.

Rate Constant Formula

The following formula is used to calculate a rate constant.

k = R / (Am × Bⁿ)
  • Where R is the reaction rate
  • A is the molar concentration of substance A
  • m is the partial order of reaction of substance A
  • B is the molar concentration of substance B
  • n is the partial order of reaction of substance B

To calculate a rate constant, divide the reaction rate by the product of the molar concentration of A raised to the power of the partial order reaction of A, times the molar concentration of B raised to the power of the partial order reaction of B.

Rate Constant Definition

For a specified reaction and temperature, the rate constant relates the measured reaction rate to the reactant concentrations through the experimentally determined rate law. Its units are concentration raised to 1 minus the overall reaction order, per unit time. Integrated modes here model a single-reactant disappearance law; Arrhenius modes assume constant parameters over the temperature range.

Rate Constant Example

How to calculate a rate constant?

  1. First, determine the concentrations of A and B.

    Calculate the molar concentration per unit volume of both reactants.

  2. Next, determine the partial orders of reaction.

    Calculate the partial orders of reaction with respect to reactants A and B.

  3. Finally, calculate the rate constant.

    Calculate the rate constant using the formula above.

FAQ

What is a reaction rate?

A reactant disappearance rate is the decrease in its concentration per unit time. A stoichiometrically normalized reaction rate also accounts for the reactant coefficient; use a rate definition consistent with the entered rate law.