Question 1

Which of the following best describes the collision model for chemical reactions?

Accepted Answer

Reactants must collide with sufficient energy and proper orientation to form products.

Question 2

A reaction has the following rate law: $$ 	ext{rate} = k[	ext{A}]^2[	ext{B}] . If $$the concentration of A is doubled and B is halved, by what factor does the rate change?

Accepted Answer

The rate increases by a factor of 2.

Question 3

Which of the following statements about the rate constant $$k is $$correct?

Accepted Answer

The units of $$k$$ depend on the overall order of the reaction.

Question 4

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

Accepted Answer

A plot of $$\ln[A] vs. $$time

Question 5

The half-life of a second-order reaction is given by which equation?

Accepted Answer

$$ t_{1/2} = \dfrac{1}{k[A]_0} $$

Question 6

A reaction has an activation energy $$E_a of 50 kJ/$$mol. According to the Arrhenius equation, what will happen to the rate constant $$k if $$the temperature increases?

Accepted Answer

The rate constant $$k$$ will increase.

Question 7

Which of the following is true about a catalyst in a chemical reaction?

Accepted Answer

A catalyst provides an alternative pathway with a lower activation energy.

Question 8

Consider the following mechanism:

Step 1: $$A + B \rightarrow C ($$slow)

Step 2: $$C \rightarrow D ($$fast)

Which step is the rate-determining step, and what does this imply about the rate law?

Accepted Answer

Step 1 is rate-determining; rate law depends on $$[A][B].$$

Question 9

Which of the following is NOT a criterion for a valid reaction mechanism?

Accepted Answer

Each elementary step must be reversible.

Question 10

Which of the following statements about dynamic equilibrium is correct?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 11

Given the reaction $$2A + B \rightleftharpoons 3C$$, which is the correct equilibrium constant expression?

Accepted Answer

$$ K = \dfrac{[C]^3}{[A]^2[B]} $$

Question 12

If the equilibrium constant $$K$$ for a reaction is much greater than 1, what does this indicate?

Accepted Answer

The reaction favors the formation of products at equilibrium.

Question 13

Which of the following substances should NOT be included in the equilibrium constant expression for a heterogeneous equilibrium?

Accepted Answer

Solids

Question 14

A reaction mixture initially contains 1.0 M A and 2.0 M B. At equilibrium, the concentration of A is 0.4 M. If the balanced equation is $$A + B \rightleftharpoons 2C$$, what is the equilibrium concentration of C?

Accepted Answer

1.2 M

Question 15

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, the reaction quotient $$Q is $$calculated to be greater than the equilibrium constant $$K. $$What will happen as the system moves toward equilibrium?

Accepted Answer

More $$N_2O_4$$ will form.

Question 16

Which of the following best describes the effect of increasing temperature on the rate of a chemical reaction?

Accepted Answer

It increases the number of collisions with energy greater than the activation energy.

Question 17

Which of the following is a correct form of the Arrhenius equation?

Accepted Answer

$$ k = Ae$$^{-E_a/RT}$$ $$

Question 18

Which of the following is a biological example of a catalyst?

Accepted Answer

Enzyme

Question 19

If a reaction mechanism contains an intermediate, how is it treated in the rate law?

Accepted Answer

It is omitted and replaced using the steady-state or pre-equilibrium approximation.

Question 20

Which of the following statements about the reaction quotient $$Q is $$correct?

Accepted Answer

$$Q$$ can be used to predict the direction a reaction will proceed to reach equilibrium.

General Chemistry II Exam 3 Study Guide: Chemical Kinetics & Equilibrium

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