Question 1

Which of the following best describes the significance of a negative value for Gibbs Free Energy ($$\Delta G \u003c 0) $$for a chemical reaction at constant temperature and pressure?

Accepted Answer

The reaction is spontaneous in the forward direction.

Question 2

For the reaction $$2NO_2(g) ightarrow 2NO(g) + O_2$(g)$$ with $$K_{eq} = 4.50 	imes 10^7$, does the reaction increase the entropy of the universe? Why?

Accepted Answer

Yes, because $$\Delta G is $$negative and the reaction is spontaneous.

Question 3

Which combination of signs for $$\Delta H$$ and $$\Delta S$$ will always result in a spontaneous reaction ($$\Delta G \u003c 0) at $$all temperatures?

Accepted Answer

$$\Delta H  0$$

Question 4

Consider the conversion of a solid into a gas. What are the expected signs for $$\Delta H$$, $$\Delta S$$, and $$\Delta G$$ for this process if it is spontaneous?

Accepted Answer

$$\Delta H \u003e 0$$, \ \Delta S \u003e 0$$, \ \Delta G \u003c 0$$

Question 5

A reaction has $$\Delta H \u003e 0$$ and $$\Delta S \u003e 0. $$Under what condition will this reaction be spontaneous?

Accepted Answer

At high temperatures only.

Question 6

If a reaction mixture is created and left to reach equilibrium, which of the following is true if $$\Delta G is $$positive?

Accepted Answer

The equilibrium mixture will contain more reactant than product.

Question 7

Given the reaction $$PCl_5(g$$) \rightleftharpoons $$PCl_3(g$$) + $$Cl_2(g$$)$$ at 25$$^\circ$$C, $$\Delta H^\circ = +92$$ kJ, which of the following statements is true?

Accepted Answer

The reaction is endothermic.

Question 8

Which of the following best explains why the combustion of butane ($$C_4H_{10}) is $$spontaneous?

Accepted Answer

It has $$\Delta H  0.$$

Question 9

Which of the following is the most accurate way to interpret a positive $$\Delta G$$ for a chemical reaction?

Accepted Answer

The reaction is nonspontaneous in the forward direction under standard conditions.

Question 10

If $$\Delta G = 0$$ for a reaction, which of the following statements is true?

Accepted Answer

The reaction is at equilibrium.

Question 11

Which of the following best describes the relationship between $$\Delta G$$, $$\Delta H$$, and $$\Delta S$$?

Accepted Answer

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

Question 12

A reaction has $$\Delta H \u003c 0$$ and $$\Delta S \u003c 0. $$When will this reaction be spontaneous?

Accepted Answer

At low temperatures only.

Question 13

Which of the following statements is true regarding the spontaneity of a reaction and the sign of $$\Delta G$$?

Accepted Answer

A negative $$\Delta G$$ means the reaction is spontaneous.

Question 14

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

Accepted Answer

$$\Delta G = 0$$

Question 15

If a reaction is nonspontaneous under standard conditions, which of the following could make it spontaneous?

Accepted Answer

Increasing the temperature if $$\Delta S \u003e 0.$$

Question 16

Which of the following best describes the effect of increasing temperature on the spontaneity of a reaction with $$\Delta H \u003e 0$$ and $$\Delta S \u003e 0$$?

Accepted Answer

The reaction becomes more spontaneous.

Gibbs Free Energy and Spontaneity of Chemical Reactions

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