Q: A 50.0 g sample of iron is heated from 20.0 $$^\circC to 80.0$$ $$^\circC. If $$the specific heat capacity of iron is 0.450 J/(g $$^\circC$$), how much heat is absorbed by the iron?

$$q = m \times \Delta T \times s = 50.0 \times (80.0 - 20.0) \times 0.450 = 1350 J$$

Q: For the reaction $$2NO(g) + Cl_2$(g) \rightarrow 2NOCl(g)$$, experimental data shows that doubling $$[NO]$$ quadruples the rate, while doubling $$[Cl_2$]$$ doubles the rate. What is the correct rate law for this reaction?

$$\text{rate} = k[NO]^2[Cl_2$]$$

Q: A reaction is first-order in reactant X with a rate constant $$k = 1.9 \times 10$$^{-2}$$ \text{ s}^{-1}. If$$ $$[X]_0 = 1.0 M$$, what is $$[X]$$ after 205 s?

$$[X] = [X]_0 e$$^{-kt}$$ = 1.0 \times e$$^{-1.9 \times 10^{-2}$$ \times 205} = 0.020 M$$

Question 1

Which of the following statements best describes an exothermic reaction?

Accepted Answer

It releases heat to the surroundings, resulting in a negative $$\Delta H.$$

Question 2

A 50.0 g sample of iron is heated from 20.0 $$^\circC to 80.0$$ $$^\circC. If $$the specific heat capacity of iron is 0.450 J/(g $$^\circC$$), how much heat is absorbed by the iron?

Accepted Answer

$$q = m 	imes \Delta T 	imes s = 50.0 	imes (80.0 - 20.0) 	imes 0.450 = 1350 J$$

Question 3

Which of the following best explains why a catalyst increases the rate of a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy, $$E_a$$, allowing more molecules to react.

Question 4

For the reaction $$2NO(g) + Cl_2$(g) \rightarrow 2NOCl(g)$$, experimental data shows that doubling $$[NO]$$ quadruples the rate, while doubling $$[Cl_2$]$$ doubles the rate. What is the correct rate law for this reaction?

Accepted Answer

$$	ext{rate} = k[NO]^2[Cl_2$]$$

Question 5

A reaction is first-order in reactant X with a rate constant $$k = 1.9 	imes 10$$^{-2}$$ 	ext{ s}^{-1}. If$$ $$[X]_0 = 1.0 M$$, what is $$[X]$$ after 205 s?

Accepted Answer

$$[X] = [X]_0 e$$^{-kt}$$ = 1.0 	imes e$$^{-1.9 	imes 10^{-2}$$ 	imes 205} = 0.020 M$$

Question 6

Which of the following is NOT a property of acids according to the Arrhenius definition?

Accepted Answer

Acids produce $$OH^-$$ ions in aqueous solution.

Question 7

A buffer solution is prepared by mixing acetic acid and sodium acetate. Which statement best describes how this buffer resists changes in pH?

Accepted Answer

The buffer neutralizes added $$H^+ by $$converting acetate to acetic acid, and neutralizes added $$OH^- by $$converting acetic acid to acetate.

Question 8

Which equation correctly relates the Gibbs free energy change ($$\Delta G$$), enthalpy change ($$\Delta H$$), and entropy change ($$\Delta S) at $$temperature $$T$$?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 9

A reaction has $$\Delta H = -100 kJ $$and $$\Delta S = -200 J/K. At $$what temperature will the reaction become non-spontaneous?

Accepted Answer

When $$T \u003e 500 K$$, since $$\Delta G = \Delta H - T\Delta S$$ and $$\Delta S is $$negative.

Question 10

Which of the following best describes Le Chatelier’s principle?

Accepted Answer

When a system at equilibrium is disturbed, it shifts to minimize the disturbance and restore equilibrium.

Question 11

The equilibrium constant $$K_c$$ for the reaction $$N_2O_4 \rightleftharpoons 2NO_2 is $$found to be 1.0 when 39.0% of $$N_2O_4 is $$dissociated in a 1.0 L container. Which calculation correctly determines $$K_c$$?

Accepted Answer

$$K_c = \frac{[NO_2$]^2}{[N_2O_4]} = \frac{(0.39 	imes 2)^2$}{1.0 - 0.39}$$

Question 12

Which of the following is the correct expression for the equilibrium constant $$K_w$$ for water at 25 $$^\circC$$?

Accepted Answer

$$K_w = [H_3O^+][OH^-] = 1 	imes 10$$^{-14}$$

Question 13

A solution has $$[OH^-] = 2.0 	imes 10$$^{-5}$$ M. What is the pH of the solution?

Accepted Answer

$$pOH = -\log(2.0 	imes 10$$^{-5}$$) = 4.70$$, $$pH = 14 - 4.70 = 9.30$$

Question 14

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

Accepted Answer

It is the slowest step in the mechanism and determines the overall rate.

Question 15

A reaction is second-order in one reactant with $$k = 2.0 	imes 10$$^{-2}$$ L/(mol·s). If $$[A]_0 = 0.340$$ mol/L, how long will it take for $$[A]$$ to decrease to 0.170$ mol/L?

Accepted Answer

$$t = \frac{1}{k} \left( \frac{1}{[A]_t} - \frac{1}{[A]_0} ight ) = \frac{1}{2.0 	imes 10$$^{-2}$$} \left( \frac{1}{0.170} - \frac{1}{0.340} ight ) = 147 s$$

Question 16

Which of the following is NOT a correct statement about the effect of temperature on equilibrium constants?

Accepted Answer

Changing temperature does not affect the equilibrium constant.

Question 17

Which of the following is the correct integrated rate law for a second-order reaction?

Accepted Answer

$$\frac{1}{[A]_t} = kt + \frac{1}{[A]_0}$$

Question 18

Which of the following is a correct statement about the common ion effect?

Accepted Answer

Adding a common ion to a solution decreases the solubility of a salt.

Chemistry II Final Exam Review: Thermochemistry, Kinetics, Equilibrium, and Acids & Bases

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