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 present is increased by 100 percent, which of the following is closest to the percent change in the 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

NOTE: Put directly proportional in nominator and inversely proportional in denominator.

RATE=\frac{A^2}{B}, (well as it's not the exact fraction it should be multiplied by some constant but we can ignore this in our case).

We are told that B increased by 100%, hence in denominator we have 2B. We want the rate to be the same. As rate is directly proportional to the SQUARE of A, A should also increase (nominator) by x percent and increase of A in square should be 2. Which means

x^2=2 -->

x\approx{1.41}, which is approximately 40% increase.

R=\frac{A^2}{B}=\frac{(1.4A)^2}{2B}=\frac{2A^2}{2B}Answer: D.

OPEN DISCUSSION OF THIS QUESTION IS HERE: the-rate-of-a-certain-chemical-reaction-is-directly-90119.html