For the reaction \(A+B \rightarrow C\), explain at least two ways in which the rate law could be zero order in chemical A.

One possible way to make the reaction zero order in chemical A is in the presence of a catalyst or an enzyme which can saturate with A. When the concentration of A increases, the catalyst or enzyme-related reaction site becomes saturated with A, so increasing the concentration of A does not affect the rate of the reaction anymore. The rate of reaction becomes independent of the concentration of A and hence the reaction becomes zero order with respect to chemical A.

Another way to make the reaction zero order in chemical A is if the rate-determining step, which is the slowest step in the reaction mechanism, does not involve chemical A. In a reaction mechanism that has multiple elementary steps, the overall rate law depends on the rate-determining step. If the slowest step in the mechanism does not involve chemical A, the rate of the reaction will be independent of the concentration of chemical A. In this scenario, the reaction order will be zero with respect to chemical A. These are two possible ways for the reaction between A and B to be zero order in chemical A. It is important to remember that the reaction order is determined by the reaction mechanism and cannot be predicted solely based on the balanced chemical equation.