Question 1

Which of the following best describes the difference between an open, closed, and isolated system in thermodynamics?

Accepted Answer

An open system exchanges both matter and energy with its surroundings, a closed system exchanges only energy, and an isolated system exchanges neither.

Question 2

According to the first law of thermodynamics, which of the following statements is correct?

Accepted Answer

The total energy of an isolated system is constant; energy can only be transferred or change its form.

Question 3

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

Accepted Answer

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

Question 4

A reaction has $$\Delta H = +5630 J/$$mol and $$\Delta S = +20.6 J/K$$·mol at $$T = 263 K. Is $$the reaction favorable, and why?

Accepted Answer

No, because $$\Delta G is $$positive.

Question 5

Which of the following best explains why ink diffuses in water even when there is no change in enthalpy?

Accepted Answer

The process increases entropy, which is favored by the second law of thermodynamics.

Question 6

Given the reaction $$A + B \rightleftharpoons C + D$$, if more A is added to the system at equilibrium, what happens to [B] according to Le Chatelier’s Principle?

Accepted Answer

[B] decreases.

Question 7

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

Accepted Answer

$$\Delta G = 0$$

Question 8

For the reaction $$A + B \rightleftharpoons C + D$$, the reaction quotient $$Q is $$given by:

Accepted Answer

$$Q = \frac{[C][D]}{[A][B]}$$

Question 9

If $$Q \u003c K$$ for a reaction, what is the favored direction and what is the sign of $$\Delta G$$?

Accepted Answer

Forward reaction is favored; $$\Delta G \u003c 0$$

Question 10

Which of the following best describes the difference between equilibrium and homeostasis in a cell?

Accepted Answer

At equilibrium, $$\Delta G = 0$$ and no net change occurs; in homeostasis, concentrations are constant but $$\Delta G 
eq 0$$ and energy input is required.

Question 11

Calculate $$\Delta G$$ for the hydrolysis of ATP at pH 7.4 and 25°C, given $$[ATP] = 5 mM$$, $$[ADP] = 0.1 mM$$, $$[$$HPO_4$$^{2-}] = 35 mM$$, and $$\Delta G$$^{\circ'}$$ = -32.2 kJ/$$mol. Use $$R = 8.314 J/($$mol·K) and $$T = 298 K.$$

Accepted Answer

$$\Delta G = -50.1 kJ/$$mol

Question 12

Which of the following factors contributes to the high free energy of hydrolysis of ATP?

Accepted Answer

Resonance stabilization of phosphate ion product

Question 13

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

Accepted Answer

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

Question 14

Which of the following is a state function?

Accepted Answer

Enthalpy

Question 15

A reaction has $$\Delta H  0. $$According to Table 3.3, how does temperature affect $$\Delta G$$?

Accepted Answer

$$\Delta G is $$negative at both low and high temperatures; the reaction is always favored.

Question 16

Which of the following best explains why your room tends to become messy over time, according to the second law of thermodynamics?

Accepted Answer

There are more ways for the room to be disordered (higher entropy) than ordered.

Question 17

Which of the following equations is used to calculate the Gibbs free energy change for the movement of a solute across a membrane?

Accepted Answer

$$\Delta G = RT \ln \frac{[A]_2}{[A]_1}$$

Question 18

Which of the following statements about standard reduction potential ($$E^{\circ'}) is $$correct?

Accepted Answer

A higher $$E^{\circ'}$$ means a greater tendency to gain electrons (be reduced).

Question 19

For the coupled reactions: $$A \rightleftharpoons B$$ ($$\Delta G$$^{\circ'}$$ = +10 kJ/$$mol) and $$C \rightleftharpoons D$$ ($$\Delta G$$^{\circ'}$$ = -30 kJ/$$mol), what is the net $$\Delta G$$^{\circ'}$$ for A + C$$ \rightarrow B + D$$?

Accepted Answer

$$\Delta G$$^{\circ'}$$ = -20 kJ/$$mol

The Energetics of Life: Thermodynamics and Free Energy in Biochemistry

Study Guide - Practice Questions

Study Guide - Flashcards