Question 1

A reaction is found to be first order in A and second order in B. Which of the following is the correct rate law for this reaction?

Accepted Answer

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

Question 2

Which of the following changes will increase the rate of a reaction according to the collision theory?

Accepted Answer

Increasing the temperature, because it increases the fraction of molecules with energy greater than the activation energy.

Question 3

The decomposition of hydrogen peroxide is catalyzed by iodide ion. Which statement best describes the role of the catalyst in this reaction?

Accepted Answer

It provides an alternative reaction pathway with a lower activation energy.

Question 4

For a first-order reaction, which of the following equations correctly relates the concentration of reactant $$[A] at $$time $$t to $$its initial concentration $$[A]_0$$ and the rate constant $$k$$?

Accepted Answer

$$ \ln{\left( \frac{[A]_0}{[A]} \right)} = kt $$

Question 5

A reaction has a rate constant $$k$$ that doubles when the temperature is increased from $$300\ \mathrm{K} to$$ $$310\ \mathrm{K}. $$Which equation would you use to calculate the activation energy $$E_a$$?

Accepted Answer

$$ \ln{\left( \frac{k_2$}{k_1$} \right)} = -\frac{E_a}{R} \left( \frac{1}{T_2$} - \frac{1}{T_1$} \right) $$

Question 6

Which of the following best describes the effect of a catalyst on a chemical equilibrium?

Accepted Answer

It increases the rate at which equilibrium is reached but does not change the position of equilibrium.

Question 7

Given the following mechanism for a reaction:
Step 1: $$A + B \rightarrow C ($$slow)
Step 2: $$C + D \rightarrow E ($$fast)
What is the rate law for the overall reaction?

Accepted Answer

$$ 	ext{rate} = k[A][B] $$

Question 8

A student measures the half-life of a radioactive isotope and finds it to be 10 minutes. What fraction of the original sample remains after 30 minutes?

Accepted Answer

$$ \frac{1}{8} $$

Question 9

Which of the following statements about the equilibrium constant $$K is $$correct?

Accepted Answer

It is constant at a given temperature and depends only on temperature.

Question 10

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, what will happen if the pressure is increased by decreasing the volume at constant temperature?

Accepted Answer

The equilibrium will shift toward the formation of $$NH_3.$$

Question 11

Which of the following is the correct expression for the equilibrium constant $$K_c$$ for the reaction $$2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)$$?

Accepted Answer

$$ K_c = \frac{[SO_3$]^2}{[SO_2$]^2[O_2$]} $$

Question 12

A reaction mixture initially contains only reactants. As the reaction proceeds, the rate of the forward reaction decreases. Why does this occur?

Accepted Answer

The concentration of reactants decreases, leading to fewer effective collisions.

Question 13

Which of the following best describes a transition state in a chemical reaction?

Accepted Answer

A high-energy, unstable arrangement of atoms at the peak of the reaction coordinate.

Question 14

For a zero-order reaction, which of the following plots will yield a straight line?

Accepted Answer

$$ [A]  vs$$. $$ t $$

Question 15

A chemical system at equilibrium is disturbed by adding more reactant. According to Le Châtelier's principle, what will happen?

Accepted Answer

The system will shift to produce more products.

Question 16

Which of the following is true about the rate-determining step in a reaction mechanism?

Accepted Answer

It is the slowest step and limits the overall reaction rate.

Question 17

For the reaction $$2NO_2(g) \rightleftharpoons 2NO(g) + O_2$(g)$$, the equilibrium constant $$K_c is$$ $$0.36 at$$ $$400\ ^\circ\mathrm{C}. $$What is the value of $$K_c$$ for the reverse reaction?

Accepted Answer

$$ 2.78 $$

Question 18

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

Accepted Answer

12

Question 19

Which of the following is a correct statement about dynamic equilibrium in a chemical reaction?

Accepted Answer

The rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

Chemical Kinetics and Chemical Equilibrium: Core Concepts and Calculations

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