Britannica Sources used in this answer

How does a zero-order reaction change as time passes?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A graph showing a potential energy curve for a chemical reaction, with the y-axis labeled potential energy and the x-axis labeled progress of reaction. The curve rises from the initial state (reactants) to a peak labeled transition state (activated complex), indicating activation energy, then drops to the final state (products). — chemical kinetics In the Arrhenius equation, the activation energy (E) represents the minimum amount of energy required to transform reactants into products in a chemical reaction. On a potential energy curve, the value of the activation energy is equivalent to the difference in potential energy between particles in an intermediate configuration (known as the activated complex, or transition state) and particles of reactants in their initial state. The activation energy thus can be visualized as a barrier that must be overcome by reactants before products can be formed.

In a zero-order reaction, the rate of the chemical reaction remains constant and is independent of the concentration of the reacting substances.12

As time ( $t$ ) passes, the concentration of the reactant ([A]) decreases linearly according to the following equation:

$[A] = [A]_{0} - k t$

In this expression, $[A]_{0}$ represents the initial concentration of the reactant, and $k$ is the rate constant. Unlike other reaction orders where the rate typically slows down as reactants are depleted, the rate of a zero-order reaction stays the same until the reactant is consumed.123