Question 1

Gibbs Free Energy ($$\Delta G) is a $$measure of what type of change in a chemical or physical process?

Accepted Answer

Energy

Question 2

Which of the following statements is true if $$\Delta G is $$small and positive for a reaction?

Accepted Answer

The reverse reaction is spontaneous and system is near equilibrium.

Question 3

If $$\Delta H is $$positive and $$\Delta S is $$positive, under what temperature conditions will a reaction be spontaneous?

Accepted Answer

At high temperatures

Question 4

For the reaction: $$\mathrm{$$PCl_5$$ (g) \rightarrow $$PCl_3$$ (g) + Cl_2$ (g)} at 25$^\circC$$, $$\Delta H = 92.50 kJ. $$Which of the following statements is true?

Accepted Answer

If the temperature is increased, the ratio $$\frac{[$$PCl_3$$][Cl_2$]}{[$$PCl_5$$]}$$ will increase.

Question 5

What are the signs of $$\Delta H$$, $$\Delta S$$, and $$\Delta G$$ for the spontaneous conversion of a solid into a gas?

Accepted Answer

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

Question 6

You calculate the value of $$\Delta G$$ for a chemical reaction and get a positive value. What is the most accurate way to interpret this result?

Accepted Answer

If a mixture of reactants and products is created and left to equilibrate, the equilibrium mixture will contain more reactant than product.

Question 7

Consider the combustion of butane gas: $$\mathrm{C_4H_{10}(g) + 13/2 O_2$(g) \rightarrow 4 CO_2$(g) + 5 H_2O(g)}. $$Predict the signs of $$\Delta S$$, $$\Delta H$$, and $$\Delta G.$$

Accepted Answer

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

Question 8

Which equation correctly relates Gibbs Free Energy to enthalpy, entropy, and temperature?

Accepted Answer

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

Question 9

For a reaction in which $$\Delta H = 125 kJ $$and $$\Delta S = 325 J/K$$, determine the temperature in Celsius above which the reaction is spontaneous.

Accepted Answer

$$385\ ^\circC$$

Question 10

A particular reaction has $$\Delta H = -350 kJ $$and $$\Delta S = -350 J/K at 24$^\circC. $$How much heat will be released/absorbed?

Accepted Answer

2,940,000 J released

Question 11

For a particular reaction, $$\Delta H = -111.4 kJ $$and $$\Delta S = -25.0 J/K. $$Calculate $$\Delta G at 298 K. $$What can be said about the spontaneity of the reaction at 298 K?

Accepted Answer

The system is spontaneous as written.

Question 12

Which of the following best describes a reaction with $$\Delta G \u003c 0$$?

Accepted Answer

The reaction is spontaneous.

Question 13

If $$\Delta H is $$negative and $$\Delta S is $$negative, when will the reaction be spontaneous?

Accepted Answer

At low temperatures

Question 14

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

Accepted Answer

$$\Delta G = 0$$

Question 15

A reaction has $$\Delta H \u003e 0$$ and $$\Delta S \u003c 0. $$What can be said about its spontaneity?

Accepted Answer

Nonspontaneous at all temperatures

Gibbs Free Energy and Spontaneity in Chemical Reactions

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