Final answer:
Changing the concentration of a zero-order reactant has no effect on the reaction rate because the rate is independent of the concentration, as described by the zero-order rate law, rate = k.
Step-by-step explanation:
When discussing the effect of changing the concentration of a reactant on the rate of a chemical reaction, it is important to understand the concept of reaction order. For a zero-order reaction, the rate of reaction is independent of the concentration of the reactants. This means that no matter how much you increase or decrease the concentration of a zero-order reactant, the reaction rate will remain constant.
Therefore, the correct answer to the question, 'What effect does changing the concentration of a zero-order reactant have on the rate?' is A. No effect. The rate law for a zero-order reaction is expressed as rate = k, where 'k' is the rate constant, and it shows that the rate does not depend on the concentration of reactants.