In a zero-order reaction, what happens to the rate if [A] is doubled?

In a zero-order reaction, what happens to the rate if [A] is doubled?

• A. Rate remains unchanged.
• B. Rate doubles.
• C. Rate halves.
• D. Rate quadruples.

Answer: (D)

In a zero-order reaction, the rate law is rate = k, with no dependence on the concentration of A. That means changing [A] has no effect on the rate; doubling [A] just leaves the rate the same at k. The constant rate is a hallmark of zero-order kinetics, where the concentration-time profile is a straight line with slope −k. For contrast, if the reaction were first-order, doubling [A] would double the rate, and if it were second-order, doubling [A] would quadruple the rate.

In a zero-order reaction, the rate law is rate = k, with no dependence on the concentration of A. That means changing [A] has no effect on the rate; doubling [A] just leaves the rate the same at k. The constant rate is a hallmark of zero-order kinetics, where the concentration-time profile is a straight line with slope −k. For contrast, if the reaction were first-order, doubling [A] would double the rate, and if it were second-order, doubling [A] would quadruple the rate.