Q.1 Which of the following is a state function?
Work
Heat
Enthalpy
Path taken
Explanation - State functions depend only on the current state of the system, not on the path taken. Enthalpy is a state function, while work and heat are path functions.
Correct answer is: Enthalpy
Q.2 The first law of thermodynamics is essentially a statement of:
Entropy change
Conservation of energy
Spontaneity of reactions
Gibbs free energy change
Explanation - The first law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another.
Correct answer is: Conservation of energy
Q.3 Which of the following processes is isothermal?
Boiling of water at 100°C
Heating ice from -10°C to 0°C
Melting of ice
All of the above
Explanation - An isothermal process occurs at constant temperature. Boiling of water, melting of ice, and heating at a phase change all occur at constant temperature.
Correct answer is: All of the above
Q.4 In an adiabatic process:
ΔQ = 0
ΔU = 0
ΔH = 0
Work done = 0
Explanation - An adiabatic process is one in which no heat is exchanged with the surroundings, so ΔQ = 0.
Correct answer is: ΔQ = 0
Q.5 Which of the following is true for an exothermic reaction?
ΔH > 0
ΔH < 0
ΔS > 0
ΔG > 0
Explanation - Exothermic reactions release heat, leading to a negative enthalpy change (ΔH < 0).
Correct answer is: ΔH < 0
Q.6 The change in internal energy (ΔU) for a system undergoing expansion against a constant external pressure is given by:
ΔU = q - w
ΔU = w - q
ΔU = q + w
ΔU = -q - w
Explanation - According to the first law, ΔU = q - w, where q is heat absorbed by the system and w is work done by the system.
Correct answer is: ΔU = q - w
Q.7 The Gibbs free energy change (ΔG) is related to spontaneity as:
ΔG < 0: non-spontaneous
ΔG > 0: spontaneous
ΔG < 0: spontaneous
ΔG = 0: spontaneous
Explanation - A reaction is spontaneous if Gibbs free energy change is negative (ΔG < 0).
Correct answer is: ΔG < 0: spontaneous
Q.8 For a reversible isothermal expansion of an ideal gas, the work done is:
nRT ln(V2/V1)
ΔU
0
ΔH
Explanation - For a reversible isothermal expansion, work done W = nRT ln(V2/V1), derived from integrating PdV.
Correct answer is: nRT ln(V2/V1)
Q.9 The enthalpy change of a reaction at constant pressure is equal to:
Heat exchanged at constant volume
Heat exchanged at constant pressure
Work done by the system
Internal energy change
Explanation - Enthalpy change ΔH equals the heat exchanged when the reaction occurs at constant pressure.
Correct answer is: Heat exchanged at constant pressure
Q.10 Which of the following increases entropy (ΔS) of a system?
Freezing of water
Condensation of steam
Dissolving salt in water
Deposition of iodine
Explanation - Dissolving a solute generally increases disorder (entropy) because ions are more randomly distributed in solution.
Correct answer is: Dissolving salt in water
Q.11 For a spontaneous reaction at all temperatures, the signs of ΔH and ΔS are:
ΔH < 0, ΔS < 0
ΔH > 0, ΔS > 0
ΔH < 0, ΔS > 0
ΔH > 0, ΔS < 0
Explanation - Spontaneous reactions have ΔG < 0. If ΔH is negative (exothermic) and ΔS is positive (entropy increases), ΔG will always be negative.
Correct answer is: ΔH < 0, ΔS > 0
Q.12 Which of the following statements about the second law of thermodynamics is correct?
Total energy of the universe decreases
Entropy of an isolated system never decreases
Enthalpy of the universe increases
Internal energy is constant
Explanation - The second law states that the entropy of an isolated system either increases or remains constant; it never decreases spontaneously.
Correct answer is: Entropy of an isolated system never decreases
Q.13 What is the maximum work obtainable from a process at constant temperature?
ΔH
ΔU
-ΔG
ΔS
Explanation - At constant temperature and pressure, the maximum useful work that can be obtained from a system is equal to the negative of the Gibbs free energy change.
Correct answer is: -ΔG
Q.14 If ΔG = 0 for a reaction, then the reaction is:
Spontaneous
Non-spontaneous
At equilibrium
Exothermic
Explanation - When ΔG = 0, there is no net change in free energy, indicating the system is at equilibrium.
Correct answer is: At equilibrium
Q.15 In a cyclic process, the net change in internal energy is:
Positive
Negative
Zero
Depends on pressure
Explanation - Internal energy is a state function, so in a cyclic process (returning to the initial state), ΔU = 0.
Correct answer is: Zero
Q.16 Which of the following represents an endothermic process?
Combustion of methane
Freezing of water
Evaporation of water
Condensation of steam
Explanation - Endothermic processes absorb heat from the surroundings. Evaporation requires energy input to break intermolecular forces.
Correct answer is: Evaporation of water
Q.17 For an ideal gas, the internal energy depends only on:
Pressure
Temperature
Volume
Pressure and volume both
Explanation - For an ideal gas, internal energy is a function of temperature only, independent of volume and pressure.
Correct answer is: Temperature
Q.18 Which of the following is true for an isobaric process?
Pressure is constant
Volume is constant
Temperature is constant
No heat is exchanged
Explanation - An isobaric process occurs at constant pressure. Heat exchange can still happen.
Correct answer is: Pressure is constant
Q.19 The Helmholtz free energy is defined as:
F = U + TS
F = H - TS
F = U - TS
F = G + TS
Explanation - Helmholtz free energy F = U - TS, where U is internal energy, T temperature, and S entropy.
Correct answer is: F = U - TS
Q.20 Which thermodynamic quantity is minimized at equilibrium for a system at constant temperature and volume?
Gibbs free energy
Enthalpy
Helmholtz free energy
Internal energy
Explanation - At constant temperature and volume, the Helmholtz free energy reaches a minimum at equilibrium.
Correct answer is: Helmholtz free energy
Q.21 The efficiency of a Carnot engine depends on:
Work done only
Temperatures of hot and cold reservoirs
Entropy change
Pressure difference
Explanation - Carnot engine efficiency = 1 - Tc/Th, depending only on the absolute temperatures of the cold and hot reservoirs.
Correct answer is: Temperatures of hot and cold reservoirs
Q.22 Which of the following is true for a spontaneous process?
ΔG > 0
ΔS_universe > 0
ΔH > 0 always
ΔU < 0 always
Explanation - Spontaneous processes increase the entropy of the universe (ΔS_universe > 0), regardless of enthalpy change.
Correct answer is: ΔS_universe > 0
Q.23 During an isothermal expansion of an ideal gas, the change in internal energy (ΔU) is:
Positive
Negative
Zero
Depends on volume
Explanation - For an ideal gas, internal energy depends only on temperature. In an isothermal process, ΔT = 0, so ΔU = 0.
Correct answer is: Zero
Q.24 Which of the following statements is correct for an irreversible process?
ΔS_total = 0
ΔS_total < 0
ΔS_total > 0
ΔU = 0
Explanation - In an irreversible process, the total entropy of the system and surroundings increases, so ΔS_total > 0.
Correct answer is: ΔS_total > 0