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 9 of 30
- A. Second
- B. First
- C. Zeroth
- D. Third
Explanation: Refrigeration transfers heat from a low-temperature region to a high-temperature region, which cannot occur spontaneously and is explained…
Correct answer: Second- A. ∞
- B. 0
- C. +ve
- D. -ve
Explanation: The Joule-Thomson coefficient is μJT = (∂T/∂P)H, and the inversion curve is defined where this coefficient changes sign.
Correct answer: 0- A. Temperature
- B. Volume
- C. Pressure
- D. None of these
Explanation: Boundary work is W = ∫p dV. At constant volume, dV = 0, so no pressure-volume work is done, assuming this is the only type of work…
Correct answer: Volume- A. Zero
- B. 50%
- C. Almost 100%
- D. unpredictable
Explanation: When air temperature is close to its dew-point temperature, it is nearly saturated with water vapour.
Correct answer: Almost 100%- A. 0
- B. -ve
- C. +ve
- D. ∞
Explanation: For an ideal gas, enthalpy depends only on temperature, so pressure throttling causes no temperature change.
Correct answer: 0- A. 1.572
- B. 1.9398
- C. 3.389
- D. 4.238
Explanation: For methanol, modified Raoult's law gives yP = xγP°; thus γ = (0.5714 × 39.223)/(0.1686 × 84.562) ≈ 1.572.
Correct answer: 1.572- A. 0
- B. 100
- C. 50
- D. ∞
Explanation: During melting or freezing at constant pressure, heat can be added or removed as latent heat while the temperature remains fixed.
Correct answer: ∞- A. V1/V2
- B. V2/V1
- C. V1 - V2
- D. V1.V2
Explanation: The compressibility factor is Z = PV/RT. At the same pressure and temperature, the ideal-gas volume is V2 = RT/P, so Z equals the ratio of…
Correct answer: V1/V2- A. Zero
- B. Two
- C. One
- D. Three
Explanation: The ordinary binary two-phase system has two degrees of freedom, but an azeotrope imposes the extra condition that liquid and vapour…
Correct answer: One- A. The surface tension vanishes
- B. Liquid and vapour have the same density
- C. There is no distinction between liquid and vapour phases
- D. All A, B. and C
Explanation: At the critical point, liquid and vapour densities become equal, surface tension vanishes, and the two phases lose their distinct…
Correct answer: All A, B. and C- A. 0
- B. 1
- C. 2
- D. 3
Explanation: Gibbs phase rule permits an invariant system with zero degrees of freedom, such as a pure substance at its triple point.
Correct answer: 0- A. -19.4
- B. -30.2
- C. 55.2
- D. -55.2
Explanation: Using ΔH = ΣH_products − ΣH_reactants gives −24.8 − [−17.9 + 12.5] = −19.4 kcal/mol.
Correct answer: -19.4- A. Specific heat
- B. Latent heat of vaporisation
- C. Specific vapor volume
- D. Viscosity
Explanation: High viscosity is undesirable because it increases frictional pressure losses and makes circulation through the refrigeration system more…
Correct answer: Viscosity174. Specific _____________ does not change during phase change at constant temperature and pressure?
- A. Gibbs energy
- B. Entropy
- C. Internal energy
- D. Enthalpy
Explanation: At constant temperature and pressure during a phase change, the two phases are in equilibrium and have equal specific Gibbs energy.
Correct answer: Gibbs energy175. A change in state involving a decrease in entropy can be spontaneous, only if ____________________?
- A. It is isenthalpic
- B. It is exothermic
- C. It takes place isothermally
- D. It takes place at constant volume
Explanation: If the system entropy decreases, spontaneity requires enough entropy increase in the surroundings, which occurs through heat release, so…
Correct answer: It is exothermic- A. Both A. & B
- B. Work done
- C. Heat absorbed
- D. Neither A. nor B
Explanation: For a constant-volume process, boundary work is W = ∫P dV = 0 because the volume does not change.
Correct answer: Heat absorbed- A. None of these
- B. 273
- C. 25
- D. 0
Explanation: Thermochemical tables conventionally assign zero standard internal energy of formation to an element in its standard state at 1 atm and…
Correct answer: 0- A. Two different gases behave similarly, if their reduced properties (i.e. P, V and T) are same
- B. The surface of separation (i. e. the meniscus) between liquid and vapour phase disappears at
- C. the critical temperature
- D. No gas can be liquefied above the critical temperature, howsoever high the pressure may be.
- E. The molar heat of energy of gas at constant volume should be nearly constant (about 3
- F. calories)
Explanation: The law of corresponding states states that substances at the same reduced pressure, reduced temperature, and reduced volume show similar…
Correct answer: Two different gases behave similarly, if their reduced properties (i.e. P, V and T) are same179. Which of the following processes cannot be made reversible even under ideal condition of operation ?
- A. Free expansion of a gas
- B. Compression of air in a compressor
- C. Expansion of steam in a turbine
- D. All (A), B. & (C)
Explanation: Free expansion occurs against no opposing pressure and produces entropy, so it cannot be reversed without leaving changes in the system or…
Correct answer: Free expansion of a gas- A. Pressure
- B. Both A. & B
- C. Temperature
- D. Neither A. nor B
Explanation: The Joule-Thomson coefficient is μJT = (∂T/∂P)H, and its value depends on both the temperature and pressure state of the fluid.
Correct answer: Both A. & B