Rate Constant Calculator

Chemistry

Calculate reaction rate constant (k) from rate law. For 1st order: k = rate/[A]. For 2nd order: k = rate/([A]²). For bimolecular: k = rate/([A][B]).

Formula

k = rate / [A]ⁿ (where n = reaction order)
  • Rate constant k relates reaction rate to concentration: rate = k[A]ⁿ[B]ᵐ...
  • 1st order: k = rate/[A]; units: s⁻¹
  • 2nd order (single reactant): k = rate/[A]²; units: L·mol⁻¹·s⁻¹
  • 2nd order (bimolecular): k = rate/([A][B]); units: L·mol⁻¹·s⁻¹
  • Always positive. Temperature-dependent (Arrhenius: k = A·e^(-Ea/RT))

Example

Inputs
  • Reaction Rate (mol/L·s): 0.05
  • Reaction Order: 1
  • Concentration [A] (mol/L): 0.1

1st order reaction at rate 0.05 mol/L·s with [A]=0.1: k = 0.05/0.1 = 0.5 s⁻¹.

Frequently asked questions

What is rate constant?
Rate constant k quantifies reaction speed. Higher k = faster reaction at same concentration.
Why does k depend on order?
Rate law depends on how many molecules must collide. Order affects units and calculation.