Final answer:
The rate equation rate = kax can be simplified to rate = kab, where x = 1.
Step-by-step explanation:
The given equation is rate = kax. According to the information provided, if the rate doubles when a is doubled, it means that the rate is directly proportional to a. So, we can write the rate equation as rate = ka. To determine the value of x, we need to analyze the given equation further.
Comparing the given equation rate = kax with the information provided, we can see that the rate is directly proportional to [A] and [B], which means that x = 1. Therefore, the equation can be simplified to rate = kab.