First Order Kinetics Definition

An order of chemical reaction in which the rate of the reaction is proportional to the amount of one reactant and is determined by its concentration.

It can be expressed using the formula

rate = kA

where k is the reaction rate constant and A is the reactant concentration.

The breakdown of N₂O₅ is an example of a first-order reaction:

N₂O₅ → 2NO₂ + 12O₂

The rate of reaction is proportional to the N₂O₅ concentration raised to the first power.