Question

For a certain reaction, the rate=$k[A]^2[B]$ when the initial concentration of A is tripled keeping concentration of B constant, the initial rate would

• A. increase by a factor of six.
• B. increase by a factor of nine.
• C. increase by a factor of three.
• D. decrease by a factor of nine.

Answer 1

Answer: (B)

increase by a factor of nine.

Answer 2

Rate R = k [A]2[B]
if [A] is tripled and [B] stays the same.
Then R' = k [3A]2 [B]
R' = 9k [A]2 [B]
R' = 9R
Hence, the initial rate is increased by nine times.
Therefore, The correct option is (B): increase by a factor of nine.