Free Chemical Engineering Thermodynamics MCQs with Answers
598 Chemical Engineering Thermodynamics MCQs from Chemical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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598 questions · page 18 of 30
- A. y = 1.44
- B. 1
- C. 0
- D. 1.66
Explanation: With the initial pressure fixed, work is maximised by maintaining the highest possible pressure during expansion, which corresponds to n =…
Correct answer: 0- A. Air cycle
- B. Vapor compression with a reversible expansion engine
- C. Ordinary vapor compression cycle
- D. Carnot cycle
Explanation: The Carnot refrigerator has the maximum possible COP for specified evaporator and condenser temperatures because both heat-transfer and…
Correct answer: Carnot cycle- A. Hydrogen
- B. Nitrogen
- C. Air
- D. Oxygen
Explanation: At ordinary atmospheric conditions, hydrogen is above its Joule-Thomson inversion temperature, so throttling produces heating rather than…
Correct answer: Hydrogen- A. Latent heat of vaporisation
- B. Chemical potential
- C. Molal boiling point
- D. Heat capacity
Explanation: For a pure substance, the molar Gibbs free energy is its chemical potential, μ = Ḡ.
Correct answer: Chemical potential- A. μ = (∂P/∂T)H
- B. μ = (∂E/∂T)H
- C. μ = (∂T/∂P)H
- D. μ = (∂E/∂P)H
Explanation: The Joule-Thomson coefficient measures the temperature change with pressure during an isenthalpic process, so μJT = (∂T/∂P)H.
Correct answer: μ = (∂T/∂P)H- A. 0
- B. ∞
- C. -ve
- D. +ve
Explanation: During throttling, dT = μJT dP and the pressure change is negative. Cooling therefore requires μJT to be positive, so a positive…
Correct answer: +ve- A. Enthalpy remains constant
- B. Entropy remains constant
- C. Temperature remains constant
- D. None of these
Explanation: Throttling is a steady-flow process with negligible heat and work transfer, making it isenthalpic, so enthalpy remains constant.
Correct answer: Enthalpy remains constant- A. Water
- B. Air
- C. Evaporative
- D. Gas
Explanation: Domestic refrigerators generally use air-cooled condensers, with room air removing the refrigerant's heat through finned tubing.
Correct answer: Air- A. Van Laar
- B. Margules
- C. Gibbs-Duhem-Margules
- D. Gibbs-Duhem
Explanation: For a binary vapour-liquid system at constant temperature and pressure, the relation between the logarithmic changes in partial pressures…
Correct answer: Gibbs-Duhem-Margules- A. Zero
- B. Positive
- C. None of these
- D. Negative
Explanation: At constant temperature and pressure, a spontaneous change has a negative change in Gibbs free energy, ΔG < 0.
Correct answer: Negative- A. -273
- B. 0
- C. -78
- D. 5
Explanation: At approximately atmospheric pressure, solid carbon dioxide sublimes at about −78.5°C, so −78°C is the nearest option.
Correct answer: -78- A. Freon-12
- B. Ammonia
- C. Ethylene
- D. Carbon dioxide
Explanation: Freon-12, ammonia, and carbon dioxide are established common refrigerants.
Correct answer: Ethylene- A. 2.73
- B. 28.3
- C. 273
- D. 283
Explanation: At constant pressure, Charles's law gives V₂/V₁ = T₂/T₁ using absolute temperature. Thus V₂ = 27.3 × 283/273 ≈ 28.3 cc, not 27.3 × 10.
Correct answer: 28.3- A. Isothermal
- B. Isobaric
- C. Polytropic
- D. Adiabatic
Explanation: For an ideal gas, PV = constant means temperature remains constant because PV = nRT.
Correct answer: Isothermal- A. Zero
- B. Negative
- C. More than zero
- D. Indeterminate
Explanation: The third law of thermodynamics assigns zero entropy at absolute zero to a perfect crystalline substance because it has one unique…
Correct answer: Zero- A. ds = 0
- B. ds > 0
- C. ds <0
- D. ds = Constant
Explanation: An isolated system exchanges neither heat nor work with its surroundings, so any spontaneous change must increase its entropy.
Correct answer: ds > 0- A. Entropy
- B. Temperature
- C. Internal energy
- D. Enthalpy
Explanation: A throttling valve operates at steady state with negligible heat transfer and shaft work, so the inlet and outlet enthalpies are equal.
Correct answer: Enthalpy- A. PV = A + B/V + C/V2 + D/V3 + ...
- B. PV = nRT
- C. (p + a/V2)(V - b) = nRT
- D. None of these
Explanation: The virial equation expresses pressure-volume behaviour as a series in inverse molar volume, such as PV = A + B/V + C/V² + ....
Correct answer: PV = A + B/V + C/V2 + D/V3 + ...- A. Entropy
- B. Gibbs free energy
- C. Enthalpy
- D. Internal energy
Explanation: At phase equilibrium, the specific Gibbs free energy, or chemical potential, is equal in the coexisting phases.
Correct answer: Gibbs free energy- A. Eutectic
- B. Plait
- C. Triple
- D. Critical
Explanation: The triple point is the unique temperature and pressure at which solid, liquid, and vapour phases coexist in equilibrium.
Correct answer: Triple