Question 1

Which of the following statements best describes the difference between thermodynamics and kinetics in a chemical reaction?

Accepted Answer

Thermodynamics determines whether a reaction is spontaneous based on initial and final states, while kinetics determines the rate at which the reaction proceeds.

Question 2

Which process results in an increase in entropy ($$\Delta S \u003e 0$$)?

Accepted Answer

Dissolving NaCl(s) in water to form Na$$^+$$ and Cl$$^-$$ ions.

Question 3

Given the reaction: $$\mathrm{N_2$(g) + 3 H_2$(g) \rightarrow 2 NH_3$(g)}$$, what is the sign of $$\Delta S_{system}$$ and why?

Accepted Answer

$$\Delta S_{system} \u003c 0$$ because the number of gas molecules decreases.

Question 4

Which equation correctly relates Gibbs free energy to enthalpy and entropy?

Accepted Answer

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

Question 5

A reaction has $$\Delta H = +95.7 kJ $$and $$\Delta S = +142.2 J/K. At $$what minimum temperature (in K) will the reaction become spontaneous?

Accepted Answer

$$T = \frac{\Delta H}{\Delta S} = \frac{95700}{142.2} = 673 K$$

Question 6

Which of the following best describes the Third Law of Thermodynamics?

Accepted Answer

The entropy of a perfect crystal at absolute zero is zero.

Question 7

For the reaction $$2 NO_2$(g) \rightleftharpoons N_2O_4(g) at 25$$°C, given $$\Delta G^\circ = -4.8 kJ$$, what can you conclude about the equilibrium constant $$K_{eq}$$?

Accepted Answer

$$K_{eq} \u003e 1$$

Question 8

Which of the following changes will always increase the entropy of a system?

Accepted Answer

Melting ice.

Question 9

A reaction is nonspontaneous at low temperature but becomes spontaneous at high temperature. Which combination of $$\Delta H$$ and $$\Delta S is $$consistent with this behavior?

Accepted Answer

$$\Delta H \u003e 0$$, $$\Delta S \u003e 0$$

Question 10

Which of the following statements about standard molar entropy ($$S^\circ) is $$correct?

Accepted Answer

Standard molar entropy increases with increasing molecular complexity.

Question 11

Which of the following reactions is expected to have a positive $$\Delta S_{system}$$?

Accepted Answer

$$NH_4NO_3(s) \rightarrow NH_4$^+(aq) + NO_3$^-(aq)$$

Question 12

Which equation relates the standard free energy change to the equilibrium constant?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 13

Which of the following best explains why the dissolution of NaCl(s) in water is spontaneous at room temperature?

Accepted Answer

The process is endothermic but the increase in entropy outweighs the enthalpy change.

Question 14

A reaction has $$\Delta H = -100 kJ $$and $$\Delta S = -200 J/K. At $$what temperature (in K) does the reaction change from spontaneous to nonspontaneous?

Accepted Answer

$$T = \frac{\Delta H}{\Delta S} = \frac{-100000}{-200} = 500 K$$

Question 15

Which of the following is true for a process at equilibrium?

Accepted Answer

$$\Delta G = 0$$

Question 16

Which of the following factors does NOT increase the entropy of a system?

Accepted Answer

Condensing a gas to a liquid.

Question 17

Which of the following best describes the effect of increasing temperature on the equilibrium constant for an exothermic reaction?

Accepted Answer

The equilibrium constant decreases.

Question 18

Which of the following is a correct statement about coupled reactions?

Accepted Answer

A nonspontaneous reaction can be driven by coupling it with a spontaneous reaction.

Question 19

Which of the following is the correct expression for the entropy change of the surroundings ($$\Delta S_{surr}) $$for a reaction at constant pressure?

Accepted Answer

$$\Delta S_{surr} = \frac{q_{surr}}{T}$$

Free Energy and Thermodynamics: Study Notes for General Chemistry

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