Question 1

Which of the following statements best describes a state function in thermodynamics?

Accepted Answer

A property that depends only on the present state of the system, not on the path taken to reach that state.

Question 2

Which equation correctly expresses the First Law of Thermodynamics for a closed system?

Accepted Answer

$$\Delta U = q + w$$

Question 3

A gas expands against a constant external pressure. Which equation gives the work done by the system?

Accepted Answer

$$w = -P_{ext} \Delta V$$

Question 4

Which of the following processes will most likely result in an increase in entropy ($$\Delta S \u003e 0$$)?

Accepted Answer

A solid melting to form a liquid.

Question 5

For the melting of ice at 273 K, the entropy change is given by which equation?

Accepted Answer

$$\Delta S = \dfrac{\Delta H_{fus}}{T}$$

Question 6

Which statement best describes the Second Law of Thermodynamics?

Accepted Answer

The total entropy of a system and its surroundings always increases for a spontaneous process.

Question 7

Which equation defines the Gibbs free energy change for a reaction under standard conditions?

Accepted Answer

$$\Delta G$$^{\circ}$$ = \Delta H$$^{\circ}$$ - T \Delta S$$^{\circ}$$

Question 8

A reaction has $$\Delta H \u003c 0$$ and $$\Delta S \u003c 0. At $$what temperature is the reaction spontaneous?

Accepted Answer

At low temperatures.

Question 9

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

Accepted Answer

$$\Delta G = 0$$

Question 10

The Boltzmann equation for entropy is:

Accepted Answer

$$S = k \ln W$$

Question 11

Which of the following reactions will likely have a positive entropy change ($$\Delta S \u003e 0$$)?

Accepted Answer

A reaction in which a solid changes to a gas.

Question 12

If $$\Delta G$$^{\circ}$$ for a reaction is a large negative number (e.g., $$\u003c-10$$ kJ/mol), what does this indicate?

Accepted Answer

The reaction is spontaneous and goes nearly to completion.

Question 13

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

Accepted Answer

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

Question 14

A chemical reaction has $$\Delta H$$^{\circ}$$ = 178.3 kJ/$$mol and $$\Delta S$$^{\circ}$$ = 159.0 J/($$mol\cdot K). At what temperature will the reaction be at equilibrium under standard conditions?

Accepted Answer

$$T = \dfrac{\Delta H$$^{\circ}$$}{\Delta S$$^{\circ}$$}$$

Question 15

Which of the following is NOT a situation where entropy usually increases?

Accepted Answer

A reaction in which a liquid freezes to a solid.

Question 16

For a process at constant pressure, which equation correctly relates enthalpy change to heat?

Accepted Answer

$$\Delta H = q_p$$

Question 17

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

Accepted Answer

A perfectly crystalline substance at 0 K has an entropy of zero.

Question 18

A reaction has $$\Delta H \u003e 0$$ and $$\Delta S \u003e 0. At $$what temperature is the reaction spontaneous?

Accepted Answer

At high temperatures.

Question 19

Which of the following is the correct expression for the maximum work obtainable from a chemical process?

Accepted Answer

$$w_{max} = \Delta G$$

Chapter 19: Thermodynamics and Equilibrium – Study Notes

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