Given the concentration-time data for a reaction, the half-life is found to be constant. What can be concluded about the order of the reaction?

The constant half-life indicates that the reaction is first-order with respect to the reactant. This answer is anchored to Rate equations and orders (A-level only).

The constant half-life indicates that the reaction is first-order with respect to the reactant. is the best answer because it directly supports the AQA A-Level Chemistry objective to interpret concentration-time graphs. This reasoning is anchored to Rate equations and orders (A-level only) in Rate equations (A-level only), and it separates concentration-time from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.