Q: For the reaction $$2NO_2(g) \rightarrow 2NO(g) + O_2$(g)$$, which expression correctly relates the rate of disappearance of $$NO_2 to $$the rate of appearance of $$O_2$$?

$$\text{Rate} = -\frac{d[NO_2$]}{dt} = 2 \frac{d[NO]}{dt} = \frac{d[O_2$]}{dt}$$

Question 1

Which of the following best describes the effect on the rate constant $$k$$ when the temperature of a reaction is increased, according to the Arrhenius equation?

Accepted Answer

The rate constant $$k$$ increases exponentially with increasing temperature.

Question 2

A reaction is found to be first order with respect to reactant A. Which integrated rate law should be used to determine the concentration of A at time $$t$$?

Accepted Answer

$$[A]_t = [A]_0 e$$^{-kt}$$

Question 3

For the reaction $$2NO_2(g) \rightarrow 2NO(g) + O_2$(g)$$, which expression correctly relates the rate of disappearance of $$NO_2 to $$the rate of appearance of $$O_2$$?

Accepted Answer

$$	ext{Rate} = -\frac{d[NO_2$]}{dt} = 2 \frac{d[NO]}{dt} = \frac{d[O_2$]}{dt}$$

Question 4

If the rate law for a reaction is $$	ext{Rate} = k[A][B]^2$$, what is the overall order of the reaction?

Accepted Answer

Third order

Question 5

Which statement best describes Le Châtelier's Principle?

Accepted Answer

A system at equilibrium will shift to counteract any imposed change in concentration, pressure, or temperature.

Question 6

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, the equilibrium constant K_c$ is given by:

Accepted Answer

$$K_c = \frac{[NH_3$]^2}{[N_2$][H_2$]^3}$$

Question 7

A reaction mechanism consists of the following steps:
Step 1: $$A + B \rightarrow C ($$slow)
Step 2: $$C \rightarrow D ($$fast)
Which step determines the overall rate law?

Accepted Answer

Step 1, because the slowest step in a mechanism is the rate-determining step.

Question 8

Which of the following changes will increase the yield of ammonia in the Haber process ($$N_2 + 3H_2$$ \rightleftharpoons 2NH_3$$) at equilibrium?

Accepted Answer

Increasing the pressure

Question 9

Given the equilibrium $$2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)$$, if the concentration of $$SO_2 is $$doubled, what happens to the equilibrium position?

Accepted Answer

The equilibrium shifts to the right, favoring products.

Question 10

Which of the following correctly relates $$K_p$$ and $$K_c$$ for the reaction $$aA(g) + bB(g) \rightleftharpoons cC(g) + dD(g)$$?

Accepted Answer

$$K_p = K_c (RT$$)^{\Delta n}$$, where $$\Delta n = (c + d) - (a + b)$$

Question 11

A second-order reaction has a half-life given by which of the following equations?

Accepted Answer

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

Question 12

Which of the following is true about the equilibrium constant $$K$$ for a reaction?

Accepted Answer

It changes only with temperature.

Question 13

For the reaction $$A \rightarrow B$$, the initial concentration of $$A is$$ $$0.50 M. $$After $$10$$ minutes, the concentration of $$A is$$ $$0.25 M. If $$the reaction is first order, what is the rate constant $$k$$?

Accepted Answer

$$k = \frac{1}{10} \ln(0.5/0.25)$$

Question 14

Which of the following is NOT a valid assumption for the steady-state approximation in reaction mechanisms?

Accepted Answer

The intermediate is present in high concentration throughout the reaction.

Question 15

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Lowering the activation energy $$E_a$$

Question 16

If the equilibrium constant $$K$$ for a reaction is much less than 1, which statement is true?

Accepted Answer

The reaction strongly favors reactants at equilibrium.

Question 17

For the reaction $$A + B \rightarrow C$$, doubling the concentration of $$A$$ doubles the rate, but doubling $$B$$ quadruples the rate. What is the rate law?

Accepted Answer

$$	ext{Rate} = k[A][B]^2$$

Question 18

Which of the following is true about the relationship between $$Q$$ and $$K$$ for a chemical reaction?

Accepted Answer

If $$Q \u003c K$$, the reaction will shift toward products to reach equilibrium.

Question 19

A student is studying the decomposition of hydrogen peroxide: $$2H_2O_2 \rightarrow 2H_2O + O_2$. If the rate of disappearance of H_2O_2$ is 0.10$ M/s, what is the rate of appearance of O_2$?

Accepted Answer

$$0.05 M/s$$

Study Guide: Chemical Kinetics and Chemical Equilibrium

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