Chemistry · Reaction Kinetics

Rate Law: Rate = k[A]^x. The unit of the rate constant (k) is typically expressed as concentration unit per time. The unit of the rate of reaction (Rate) is also in concentration unit per time. Therefore, in a zero-order reaction, the unit of the rate constant is the same as the unit of the rate of reaction.

In a first-order reaction, the rate law is expressed as Rate = k[A]. The unit of the rate constant (k) is time^-1, while the unit of the rate of reaction is concentration unit per time, such as mol dm^-3 s^-1. Therefore, the units are not the same.

In a zero-order reaction, the rate law is Rate = k. The rate constant (k) has the same unit as the rate of reaction, which is usually concentration unit per time, such as mol dm^-3 s^-1. Thus, the units match.

For a second-order reaction, the rate law might be Rate = k[A]². The unit of the rate constant (k) is typically (concentration unit)^-1 * time^-1, whereas the rate of reaction is concentration unit per time. Therefore, the units do not match.

In a third-order reaction, the rate law can be expressed as Rate = k[A]³. The unit of the rate constant (k) is (concentration unit)^-2 * time^-1. The rate of reaction has a unit of concentration unit per time. Clearly, the units are not the same.