Q: The decomposition of hydrogen peroxide, $$2H_2O_2 \rightarrow 2H_2O + O_2$, is monitored and the concentration of H_2O_2$ drops from 0.80 M to 0.60 M in 40 seconds. What is the average rate of disappearance of H_2O_2$ over this interval?

$$5.0 \times 10$$^{-3}$$\ \text{M/s}$$

Q: A mixture at equilibrium contains $$[A] = 0.20\ \text{M}$$, $$[B] = 0.30\ \text{M}$$, and $$[C] = 0.10\ \text{M}$$ for the reaction $$A + 2B \rightleftharpoons C. $$What is the value of $$K_c$$?

$$K_c = \frac{[C]}{[A][B]^2} = \frac{0.10}{0.20 \times (0.30)^2$} = 5.56$$

Q: For the reaction $$2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)$$, $$K_p is $$related to $$K_c by $$which of the following equations?

$$K_p = K_c(RT$$)^{\Delta n}$$,\ where\ \Delta n = \text{moles of gaseous products} - \text{moles of gaseous reactants}$

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

The decomposition of hydrogen peroxide, $$2H_2O_2 \rightarrow 2H_2O + O_2$, is monitored and the concentration of H_2O_2$ drops from 0.80 M to 0.60 M in 40 seconds. What is the average rate of disappearance of H_2O_2$ over this interval?

Accepted Answer

$$5.0 	imes 10$$^{-3}$$\ 	ext{M/s}$$

Question 3

For a first-order reaction, the half-life is given by which of the following equations?

Accepted Answer

$$t_{1/2} = \frac{0.693}{k}$$

Question 4

A reaction has a rate constant $$k$$ that increases from $$1.2 	imes 10$$^{-3}$$\ 	ext{s}^{-1} at$$ $$300\ 	ext{K} to$$ $$4.8 	imes 10$$^{-3}$$\ 	ext{s}^{-1} at$$ $$320\ 	ext{K}. $$Using the Arrhenius equation, which of the following best explains this observation?

Accepted Answer

The activation energy is overcome more frequently at higher temperature, increasing $$k.$$

Question 5

Which of the following statements about catalysts is correct?

Accepted Answer

A catalyst lowers the activation energy and increases the rate of both the forward and reverse reactions.

Question 6

Given the equilibrium reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, which of the following is the correct expression for the equilibrium constant K_c$?

Accepted Answer

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

Question 7

A mixture at equilibrium contains $$[A] = 0.20\ 	ext{M}$$, $$[B] = 0.30\ 	ext{M}$$, and $$[C] = 0.10\ 	ext{M}$$ for the reaction $$A + 2B ightleftharpoons C. $$What is the value of $$K_c$$?

Accepted Answer

$$K_c = \frac{[C]}{[A][B]^2} = \frac{0.10}{0.20 	imes (0.30)^2$} = 5.56$$

Question 8

For the reaction $$2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)$$, $$K_p is $$related to $$K_c by $$which of the following equations?

Accepted Answer

$$K_p = K_c(RT$$)^{\Delta n}$$,\ where\ \Delta n = 	ext{moles of gaseous products} - 	ext{moles of gaseous reactants}$

Question 9

A system at equilibrium is disturbed by increasing the concentration of a reactant. According to Le Chatelier’s Principle, what will happen?

Accepted Answer

The system will shift to produce more products to counteract the change.

Question 10

Which of the following is a correct statement about the effect of a catalyst on a chemical equilibrium?

Accepted Answer

A catalyst speeds up the attainment of equilibrium but does not change the position of equilibrium.

Question 11

Which of the following is a Bronsted-Lowry acid?

Accepted Answer

$$H_2SO_4$$, because it donates a proton ($$H^+) in $$aqueous solution.

Question 12

What is the pH of a $$0.010\ 	ext{M}$$ solution of $$HCl (a $$strong acid)?

Accepted Answer

$$pH = 2.00$$

Question 13

Which of the following best describes the autoionization of water?

Accepted Answer

$$2H_2O \rightleftharpoons H_3O^+ + OH^-$$

Question 14

A $$0.20\ 	ext{M}$$ solution of a weak acid $$HA$$ has a pH of 2.70. What is the value of $$K_a$$ for this acid?

Accepted Answer

$$K_a = 2.0 	imes 10$$^{-5}$$

Question 15

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

$$NaF$$

Question 16

Which of the following statements about the relationship between acid strength and conjugate base strength is correct?

Accepted Answer

The stronger the acid, the weaker its conjugate base.

Question 17

Which of the following is a Lewis acid?

Accepted Answer

$$Al^{3+}$$, because it can accept an electron pair.

Question 18

A solution has $$[OH^-] = 1.0 	imes 10$$^{-5}$$\ 	ext{M}. $$What is the pH of the solution?

Accepted Answer

$$pH = 9.00$$

Question 19

Which of the following best explains why $$HF is a $$weak acid while $$HCl is a $$strong acid?

Accepted Answer

The $$H-F$$ bond is stronger and less polar than the $$H-Cl$$ bond, making $$HF$$ less likely to ionize.

Exam 2 Study Guide: Chemical Kinetics, Equilibrium, and Acids & Bases

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