Free Chemical Engineering Thermodynamics MCQs with Answers

• A. ∞
• B. > 0
• C. < 0
• D. 0

Explanation: An isolated system has no heat or mass exchange, so the entropy balance reduces to entropy generation.

• A. The heat of formation of a compound is defined as the heat of reaction leading to the
• B. the temperature of the liquid will increase
• C. A process is irreversible as long as Δ S for the system is greater than zero
• D. The mechanical work done by a system is always equal to∫P.dV
• E. If an insoluble gas is passed through a volatile liquid placed in a perfectly insulated container,
• F. formation of the compound from its reactants

Explanation: The intended final statement defines heat of formation as the heat effect for forming a compound from its constituent reactants, normally…

• A. Second
• B. First
• C. Zeroth
• D. Third

Explanation: The second law provides the entropy criterion that determines whether a process is spontaneous and its permitted direction.

• A. Decrease
• B. Increase
• C. Remain same
• D. Increase in summer and will decrease in winter

Explanation: An operating refrigerator removes heat from its interior but rejects that heat plus the compressor's work into the room.

• A. Adiabatic expansion
• B. Joule-Thomson effect
• C. Both A. and B
• D. Neither A. nor B

Explanation: Gas liquefaction commonly uses cooling by adiabatic expansion and the Joule-Thomson effect.

• A. Decreases
• B. Decreases logarithmically
• C. Remains constant
• D. Increases

Explanation: At constant pressure, increasing reduced temperature generally makes a gas behave more ideally, so its fugacity coefficient moves toward…

• A. Less pronounced
• B. Data insufficient, can't be predicted
• C. Equal
• D. More pronounced

Explanation: For an ideal vapour-compression cycle, COP is approximately proportional to evaporator temperature divided by the difference between…

• A. Heating takes place
• B. Cooling takes place
• C. Pressure is constant
• D. Temperature is constant

Explanation: In a reversible adiabatic process, entropy remains constant, and expansion causes the gas to do work without receiving heat.

• A. dW - dE = Tds
• B. dE - dW = Tds
• C. Tds = dE + dW
• D. Tds - dW + dE >0

Explanation: Using the convention that work is done by the system, the first law gives dE = dQ - dW.

• A. Isolated
• B. Open
• C. Insulated
• D. Closed

Explanation: A closed system can exchange energy as heat or work but cannot exchange mass with its surroundings.

• A. Ideal
• B. Real
• C. Isotonic
• D. None of these

Explanation: An ideal solution has zero enthalpy and volume changes on mixing, so dilution also produces no heat effect.

• A. Less
• B. More
• C. Same
• D. Data insufficient to predict

Explanation: At the same compression ratio, the Otto cycle has greater efficiency than the Diesel cycle because heat addition at constant volume gives…

• A. Remains unchanged
• B. Decreases
• C. Increases
• D. First decreases and then increases

Explanation: For real gases at pressures above atmospheric pressure, intermolecular effects generally make the isobaric heat capacity increase with…

• A. Reversible and adiabatic
• B. Isothermal and irreversible
• C. Reversible and isothermal
• D. Adiabatic and irreversible

Explanation: An isentropic process has constant entropy and, in the standard engineering model, is both adiabatic and reversible.

• A. Unity
• B. Zero
• C. That of the heat of reaction
• D. Infinity

Explanation: The temperature derivative of Helmholtz free energy is related to entropy, since (∂F/∂T)V = −S.

• A. More
• B. Less
• C. Same
• D. Unpredictable; depends on the particular reaction

Explanation: The relation qP − qV = Δn_gRT applies when gaseous moles change, but solids and liquids have negligible volume changes.

• A. Less than
• B. More than
• C. Not related to
• D. Same as

Explanation: Decomposition and formation are reverse processes, so their heats have equal magnitudes and opposite signs.

• A. Below
• B. At
• C. Above
• D. Either B. or C.

Explanation: A gas cools during Joule-Thomson expansion when its Joule-Thomson coefficient is positive, which occurs below the inversion temperature.

• A. P + F - C = 2
• B. C = P - F + 2
• C. F = C - P - 2
• D. P = F - C - 2

Explanation: Gibbs phase rule is F = C - P + 2. Rearranging gives P + F - C = 2, so option a is the equivalent form.

• A. Minimum
• B. Indeterminate
• C. Maximum
• D. Zero

Explanation: A reversible adiabatic process has no heat transfer, and reversibility makes entropy generation zero; therefore dS = 0 and the entropy…