Q.1 Which of the following is a state function?
Work
Heat
Enthalpy
Path
Explanation - Enthalpy is a state function because its value depends only on the state of the system, not on the path taken to reach that state.
Correct answer is: Enthalpy
Q.2 According to the first law of thermodynamics, the change in internal energy of a system is equal to:
Work done by the system only
Heat added to the system only
Heat added minus work done
Sum of heat added and work done on the system
Explanation - The first law states ΔU = q + w, where ΔU is the change in internal energy, q is heat added, and w is work done on the system.
Correct answer is: Sum of heat added and work done on the system
Q.3 In an isothermal process for an ideal gas, the internal energy change is:
Positive
Negative
Zero
Depends on pressure
Explanation - For an ideal gas, internal energy depends only on temperature. In an isothermal process, temperature remains constant, so ΔU = 0.
Correct answer is: Zero
Q.4 The entropy of a perfect crystal at absolute zero is:
Zero
Infinite
Negative
Depends on volume
Explanation - According to the third law of thermodynamics, the entropy of a perfect crystal at 0 K is zero.
Correct answer is: Zero
Q.5 Which thermodynamic process occurs at constant pressure?
Isochoric
Isobaric
Adiabatic
Isothermal
Explanation - An isobaric process occurs at constant pressure, allowing heat exchange to change the enthalpy of the system.
Correct answer is: Isobaric
Q.6 Which equation represents the Gibbs free energy change?
ΔG = ΔH + TΔS
ΔG = ΔH − TΔS
ΔG = ΔU − PΔV
ΔG = q − w
Explanation - Gibbs free energy, ΔG, is defined as ΔG = ΔH − TΔS, where ΔH is enthalpy change and ΔS is entropy change.
Correct answer is: ΔG = ΔH − TΔS
Q.7 For a spontaneous process at constant temperature and pressure, ΔG is:
Positive
Negative
Zero
Undefined
Explanation - A process is spontaneous if the Gibbs free energy change ΔG is negative at constant T and P.
Correct answer is: Negative
Q.8 Which of the following is NOT a type of thermodynamic process?
Isothermal
Isobaric
Isochoric
Isometric
Explanation - 'Isometric' is not a standard thermodynamic process term; the correct term for constant volume is 'isochoric'.
Correct answer is: Isometric
Q.9 The enthalpy change for a chemical reaction at constant pressure is equal to:
ΔU
q_p
w
ΔS
Explanation - At constant pressure, the heat absorbed or released equals the enthalpy change, ΔH = q_p.
Correct answer is: q_p
Q.10 In an adiabatic process:
Heat is absorbed
Heat is released
No heat exchange occurs
Work is zero
Explanation - An adiabatic process is defined as one in which there is no heat transfer between the system and surroundings (q = 0).
Correct answer is: No heat exchange occurs
Q.11 Which law relates the internal energy change to heat and work?
Zeroth law
First law
Second law
Third law
Explanation - The first law of thermodynamics states ΔU = q + w, linking internal energy change to heat and work.
Correct answer is: First law
Q.12 In a reversible isothermal expansion of an ideal gas, the work done is:
Zero
nRT ln(Vf/Vi)
PΔV
ΔU
Explanation - For an isothermal reversible expansion, W = nRT ln(Vf/Vi), where Vi and Vf are initial and final volumes.
Correct answer is: nRT ln(Vf/Vi)
Q.13 Which of the following quantities is path-dependent?
Internal energy
Enthalpy
Entropy
Work
Explanation - Work depends on the specific path taken during a process, unlike state functions such as internal energy or enthalpy.
Correct answer is: Work
Q.14 The Helmholtz free energy is defined as:
A = U + TS
A = U − TS
A = H − TS
A = G − TS
Explanation - Helmholtz free energy, A, is given by A = U − TS, useful for systems at constant temperature and volume.
Correct answer is: A = U − TS
Q.15 The maximum work obtainable from a system at constant temperature and volume is given by:
ΔU
ΔH
ΔA
ΔG
Explanation - At constant temperature and volume, the Helmholtz free energy change ΔA equals the maximum work obtainable.
Correct answer is: ΔA
Q.16 Which of the following statements is true for an isolated system?
ΔU = 0 and ΔS = 0 always
No exchange of heat, work, or matter
ΔS decreases
ΔH = 0
Explanation - An isolated system cannot exchange heat, work, or matter with the surroundings, but its internal energy and entropy may change internally.
Correct answer is: No exchange of heat, work, or matter
Q.17 For a spontaneous process at constant temperature and volume, which free energy is used?
Gibbs free energy
Helmholtz free energy
Enthalpy
Internal energy
Explanation - At constant temperature and volume, spontaneity is determined by the Helmholtz free energy ΔA; ΔA < 0 indicates a spontaneous process.
Correct answer is: Helmholtz free energy
Q.18 The change in entropy for an ideal gas during an isothermal expansion is:
Zero
nR ln(Vf/Vi)
nCvΔT
ΔH/T
Explanation - For an ideal gas in an isothermal process, ΔS = nR ln(Vf/Vi), where Vi and Vf are initial and final volumes.
Correct answer is: nR ln(Vf/Vi)
Q.19 Which of the following represents the second law of thermodynamics?
ΔU = q + w
ΔS ≥ 0 for isolated systems
ΔH = q_p
ΔG = ΔH − TΔS
Explanation - The second law states that the entropy of an isolated system never decreases; ΔS ≥ 0.
Correct answer is: ΔS ≥ 0 for isolated systems
Q.20 In a cyclic process, the net change in internal energy is:
Positive
Negative
Zero
Depends on process type
Explanation - Internal energy is a state function, so for a cyclic process that returns to its initial state, ΔU = 0.
Correct answer is: Zero
Q.21 Which of the following processes is both adiabatic and reversible?
Isothermal expansion
Free expansion
Isentropic process
Isochoric heating
Explanation - An isentropic process is reversible and adiabatic, implying no heat transfer and constant entropy.
Correct answer is: Isentropic process
Q.22 The heat capacity at constant pressure is always:
Equal to Cv
Greater than Cv
Less than Cv
Independent of Cv
Explanation - Cp > Cv for gases because at constant pressure, work is done during expansion, requiring more heat to raise the temperature.
Correct answer is: Greater than Cv
Q.23 Which statement correctly describes enthalpy?
ΔH = ΔU + PΔV
ΔH = ΔU − PΔV
ΔH = ΔG + TΔS
ΔH = q_v
Explanation - Enthalpy H is defined as H = U + PV. At constant pressure, ΔH equals heat added.
Correct answer is: ΔH = ΔU + PΔV
Q.24 Which of the following is true for a spontaneous adiabatic process?
ΔS = 0
ΔS > 0
ΔS < 0
ΔU = 0
Explanation - For a spontaneous adiabatic process, entropy of the system increases (ΔS > 0) since no heat is exchanged.
Correct answer is: ΔS > 0
Q.25 Which of the following is the correct expression for work done in an isobaric process?
w = PΔV
w = ΔU
w = ΔH
w = 0
Explanation - In an isobaric process, work done by the system is the product of pressure and change in volume, w = PΔV.
Correct answer is: w = PΔV