Reaction Mechanism

To determine how the rate of reaction changes when the concentration of A is doubled, we start by considering the rate law for the reaction . Assuming a general rate law of the form , where is the rate of reaction, is the rate constant, and and are the reaction orders with respect to and respectively.

Since the concentration of B is kept constant, our focus is on the relationship between and the rate of reaction. From the stoichiometry of the reaction, it's typical to assume that the reaction order for is equal to its coefficient in the balanced equation, which is 2. Hence, the rate law can be approximated as , and simplifying with constant into .

Now, if the concentration of A is doubled, the new rate of reaction will be:

.

This indicates that doubling the concentration of A causes the rate of reaction to increase by a factor of four, or the rate is quadrupled.