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Multiple Choice
The rate law for a particular mechanism is expressed as rate = [A]2[B]. If [A] is halved and [B] is doubled, how would the overall rate be affected?
A
The new rate would be doubled.
B
The new rate would be four times the original rate.
C
The new rate would be one-quarter of the original rate.
D
The new rate would be one-half of the original rate.
E
The new rate would be the same as the original rate.
Verified step by step guidance
1
Identify the given rate law: rate = [A]^2[B]. This indicates that the rate is proportional to the square of the concentration of A and directly proportional to the concentration of B.
Understand the changes in concentrations: [A] is halved, which means the new concentration of A is 0.5[A]. [B] is doubled, so the new concentration of B is 2[B].
Substitute the new concentrations into the rate law: rate_new = (0.5[A])^2 * (2[B]).
Simplify the expression: (0.5[A])^2 becomes 0.25[A]^2, and multiplying by 2[B] gives 0.25 * 2 * [A]^2[B].
Calculate the factor by which the rate changes: 0.25 * 2 = 0.5. Therefore, the new rate is 0.5 times the original rate, meaning the rate is halved.