Q: A sample of 1.00 mol of argon gas undergoes an isothermal reversible expansion at 20.0°C from 10.0 dm³ to 30.0 dm³. What is the work done by the gas? (Use $$R = 8.314 J K$^{-1}$$ mol$$^{-1})$$

$$w = -8.314 \times 293.15 \times \ln(3) \approx -2670 J$$

Q: A 55 W electric heater is used to heat a gas in a constant-volume adiabatic container for 120 s, raising the temperature by 5.0°C. What is the heat capacity of the sample?

$$C = \frac{P \times t}{\Delta T} = \frac{55 \times 120}{5.0} = 1320 J K$^{-1}$$

Q: For a reversible adiabatic expansion of a perfect gas, which of the following relationships holds?

$$pV^{\gamma}$$ = \text{constant}$$

Q: Which of the following is the correct expression for the standard enthalpy of vaporization of water at 373 K?

$$\$$Delta_{vap}$$H^\circ (373\ \text{K}) = +40.66\ \text{kJ mol}^{-1}$$

Question 1

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

Accepted Answer

An open system allows transfer of both energy and matter; a closed system allows only energy transfer; an isolated system allows neither energy nor matter transfer.

Question 2

Which equation correctly represents the work done by a gas during an isothermal, reversible expansion from volume $$V_i to$$ $$V_f at $$temperature $$T$$?

Accepted Answer

$$w = -nRT \ln \frac{V_f}{V_i}$$

Question 3

A sample of 1.00 mol of argon gas undergoes an isothermal reversible expansion at 20.0°C from 10.0 dm³ to 30.0 dm³. What is the work done by the gas? (Use $$R = 8.314 J K$^{-1}$$ mol$$^{-1})$$

Accepted Answer

$$w = -8.314 	imes 293.15 	imes \ln(3) \approx -2670 J$$

Question 4

Which of the following is NOT an assumption of the ideal gas model?

Accepted Answer

Gas molecules have significant intermolecular forces.

Question 5

According to the equipartition theorem, what is the average translational kinetic energy per mole of a monatomic ideal gas at temperature $$T$$?

Accepted Answer

$$E_{trans,m} = \frac{3}{2}RT$$

Question 6

Which process is characterized by $$q = 0$$ and $$\Delta U = w$$?

Accepted Answer

Adiabatic process

Question 7

A 55 W electric heater is used to heat a gas in a constant-volume adiabatic container for 120 s, raising the temperature by 5.0°C. What is the heat capacity of the sample?

Accepted Answer

$$C = \frac{P 	imes t}{\Delta T} = \frac{55 	imes 120}{5.0} = 1320 J K$^{-1}$$

Question 8

Which of the following correctly expresses the relationship between the heat capacities at constant pressure and constant volume for a perfect gas?

Accepted Answer

$$C_p - C_V = nR$$

Question 9

For a reversible adiabatic expansion of a perfect gas, which of the following relationships holds?

Accepted Answer

$$pV^{\gamma}$$ = 	ext{constant}$$

Question 10

Which of the following best describes the entropy change ($$\Delta S) $$for a reversible process at constant temperature?

Accepted Answer

$$\Delta S = \frac{q_{rev}}{T}$$

Question 11

Which of the following is the correct expression for the standard enthalpy of vaporization of water at 373 K?

Accepted Answer

$$\$$Delta_{vap}$$H^\circ (373\ 	ext{K}) = +40.66\ 	ext{kJ mol}^{-1}$$

Question 12

Which of the following is a correct application of Hess's Law?

Accepted Answer

The enthalpy change for a reaction is the sum of the enthalpy changes for any sequence of reactions that add up to the overall reaction.

Question 13

Which of the following best describes the third law of thermodynamics?

Accepted Answer

The entropy of all perfect crystalline substances is zero at $$T = 0 K.$$

Question 14

A reaction has $$\Delta H  0. $$What can be said about the spontaneity of the reaction at all temperatures?

Accepted Answer

The reaction is spontaneous at all temperatures.

Question 15

Which of the following is the correct statistical definition of entropy according to Boltzmann?

Accepted Answer

$$S = k \ln W$$

Question 16

Which of the following best explains why the heat capacity at constant pressure ($$C_p) is $$greater than at constant volume ($$C_V) $$for a gas?

Accepted Answer

At constant pressure, the system does work as it expands, requiring more heat to achieve the same temperature change.

Question 17

Which of the following is an example of an extensive property?

Accepted Answer

Internal energy ($$U)$$

Question 18

For a linear polyatomic molecule (e.g., CO$$_2$$), what is the total number of quadratic degrees of freedom contributing to its internal energy (excluding vibrational modes at room temperature)?

Accepted Answer

5 (3 translational + 2 rotational)

Question 19

Which of the following best describes the energy level separations for molecular motions, as shown in the provided diagram?

Accepted Answer

Translational energy levels are nearly continuous, rotational levels are closely spaced, vibrational levels are more widely spaced, and electronic levels are the most widely spaced.

Chemical Thermodynamics: Foundations and Applications in Physical Chemistry

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