The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical a present and inversely proportional to the concentration of chemical b present. if the concentration of chemical b is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical a required to keep the reaction rate unchanged? a. 100% decrease b. 50% decrease c. 40% decrease d. 40% increase e. 50% increase