AP Chemistry: Kinetics & Chemical Equilibrium 2

Question 1

For the reaction rate = k[A]^2[B], what happens to the rate if [A] is tripled while [B] is held constant?

Accepted Answer

Rate increases 9x

Answer

Since A is second order, tripling [A] gives 3^2 = 9 times the rate.

Question 2

A reaction is first order in a reactant with a half-life of 20 seconds. How much of the reactant remains after 60 seconds?

Accepted Answer

1/8

Answer

60 seconds is three half-lives, so (1/2)^3 = 1/8 remains.

Question 3

Which statement about a catalyst is correct?

Accepted Answer

It lowers the activation energy of both forward and reverse reactions

Answer

A catalyst provides a lower-energy pathway, speeding both directions equally without changing K.

Question 4

For a first-order reaction, which plot yields a straight line?

Accepted Answer

ln[A] versus time

Answer

A first-order integrated rate law gives a linear plot of ln[A] versus time.

Question 5

The rate constant k of a reaction increases with temperature primarily because

Accepted Answer

more molecules have energy exceeding the activation energy

Answer

Higher temperature raises the fraction of collisions with sufficient energy to react.

AP Practice Test