Question 1

Which of the following best describes entropy ($$S) in $$the context of thermodynamics?

Accepted Answer

Entropy is a measure of the randomness or disorder of a system.

Question 2

According to the Second Law of Thermodynamics, which statement is correct for any spontaneous process?

Accepted Answer

The total entropy of the universe increases ($$\Delta S_{univ} \u003e 0).$$

Question 3

Which equation correctly relates the entropy of a system to the number of microstates ($$Q$$)?

Accepted Answer

$$S = k_b \ln Q$$

Question 4

A chemical reaction has $$\Delta H  0. $$What can be said about its spontaneity?

Accepted Answer

The reaction is spontaneous at all temperatures.

Question 5

Which of the following changes will result in an increase in entropy ($$S$$)?

Accepted Answer

Melting a solid to form a liquid.

Question 6

Given the reaction: $$2 	ext{C}_2	ext{H}_4(g) + 	ext{H}_2(g) ightarrow 	ext{C}_4	ext{H}_{10}(g)$$, and the following standard molar entropies: $$S^\circ(	ext{C}_4	ext{H}_{10}) = 310.03 J/$$mol·K, $$S^\circ(	ext{C}_2	ext{H}_4) = 219.5 J/$$mol·K, $$S^\circ(	ext{H}_2) = 130.6 J/$$mol·K, calculate $$\Delta S^\circ$$ for the reaction.

Accepted Answer

$$\Delta S^\circ = -59.57 J/K$$

Question 7

Which of the following is true about the Gibbs free energy change ($$\Delta G) $$for a spontaneous process at constant temperature and pressure?

Accepted Answer

$$\Delta G \u003c 0$$

Question 8

The melting of ice at room temperature is spontaneous. Which combination of $$\Delta H$$ and $$\Delta S$$ best explains this?

Accepted Answer

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

Question 9

At what temperature does a reaction change from spontaneous to nonspontaneous if $$\Delta H = 7700 J/$$mol and $$\Delta S = 19 J/$$mol·K?

Accepted Answer

$$T = 410 K$$

Question 10

Which statement best explains why recycled PET is not used for food and beverage containers?

Accepted Answer

Recycled PET is not allowed due to possible contamination fears.

Question 11

Which of the following is a consequence of the Third Law of Thermodynamics?

Accepted Answer

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

Question 12

Which formula is used to calculate the standard entropy change ($$\Delta S^\circ) $$for a chemical reaction?

Accepted Answer

$$\Delta S^\circ = \sum S^\circ_{products} - \sum S^\circ_{reactants}$$

Question 13

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

Accepted Answer

At high temperatures.

Question 14

Which of the following best describes the difference between reversible and irreversible processes in thermodynamics?

Accepted Answer

Reversible processes allow the system to return to its initial state with a small change in a variable.

Question 15

Which equation defines the Gibbs free energy ($$G$$)?

Accepted Answer

$$G = H - TS$$

Question 16

Why is the recycling rate of aluminum cans higher than that of PET bottles?

Accepted Answer

Recycled aluminum has the same physical properties as virgin aluminum and is easier to process.

Question 17

Which of the following is NOT a reason why recycling plastics is less economically favored than recycling aluminum?

Accepted Answer

Recycled plastics are always allowed in food containers.

Question 18

For the reaction $$	ext{CH}_4 + 2	ext{O}_2 ightarrow 	ext{CO}_2 + 2	ext{H}_2	ext{O}$$, which statement is true regarding spontaneity?

Accepted Answer

The reaction is spontaneous after initiation and proceeds in one direction.

Question 19

If a reaction has $$\Delta H \u003c 0$$ and $$\Delta S \u003c 0$$, when will it be spontaneous?

Accepted Answer

At low temperatures.

Entropy and the Laws of Thermodynamics: Chemistry and Engineering Applications

Study Guide - Practice Questions

Study Guide - Flashcards