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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- A. √(λb/Tb)
- B. Tb/λb
- C. λb/Tb
- D. √(Tb/λb)
Explanation: Trouton’s ratio is the molal latent heat of vaporisation divided by the absolute normal boiling temperature, λb/Tb.
Correct answer: λb/Tb182. The enthalpy change when ammonia gas is dissolved in water is called the heat of___________________?
- A. Combustion
- B. Formation
- C. Dilution
- D. Solution
Explanation: The enthalpy change accompanying dissolution of ammonia gas in water is the heat of solution.
Correct answer: Solution- A. Both A. and B
- B. The boiling point of a liquid
- C. The melting point of wax
- D. Neither A. nor B
Explanation: Increasing pressure raises a liquid’s boiling point because a higher temperature is needed for its vapour pressure to match the pressure.
Correct answer: Both A. and B- A. T = [RT/(V- b)] - [a/√T. V(V + b)]
- B. PV/RT = 1 + (B/V) + (C/V2) + ......
- C. n1u2 + μ2μ1 = 0
- D. None of these
Explanation: The virial equation expresses the compressibility factor as a series in inverse molar volume: PV/RT = 1 + B/V + C/V² + ….
Correct answer: PV/RT = 1 + (B/V) + (C/V2) + ......- A. 5 & 3
- B. 3.987 & 1.987
- C. 1.987 & 0.66
- D. 0.66 & 1.987
Explanation: For a monatomic ideal gas, Cv = 3R/2 and Cp = 5R/2. Using R ≈ 1.987 kcal/(kg mol·K) gives approximately Cp = 5 and Cv = 3, so option a…
Correct answer: 5 & 3- A. Lowest
- B. Highest
- C. Average
- D. None of these
Explanation: The eutectic temperature is the lowest temperature at which the liquid phase can exist in the system; below it, the components are…
Correct answer: Lowest- A. Molecular size
- B. Temperature
- C. Volume
- D. Pressure
Explanation: For an ideal gas, intermolecular effects are absent, so internal energy is a function of temperature alone, U = U(T).
Correct answer: Temperature- A. 6738.9
- B. 6753.5
- C. 7058.3
- D. 9000
Explanation: For the compressed liquid, fugacity changes approximately as f = fsat exp[Vl(P − Psat)/(RT)].
Correct answer: 6753.5- A. Clausius-Clapeyron Equation
- B. Maxwell's equation
- C. Van Laar equation
- D. Nernst Heat Theorem
Explanation: The Clausius–Clapeyron equation relates the slope of a vapour-pressure curve to latent heat, so vapour pressures at two temperatures can…
Correct answer: Clausius-Clapeyron Equation- A. High thermal conductivity
- B. High viscosity
- C. Large latent heat of vaporisation
- D. Low freezing point
Explanation: A good refrigerant should flow easily through pipes and compressors, so low viscosity is preferred.
Correct answer: High viscosity- A. 0
- B. 1
- C. 2
- D. 3
Explanation: For ice, liquid water, and vapour at equilibrium, the phase rule gives F = C − P + 2 = 1 − 3 + 2 = 0.
Correct answer: 0- A. Increases
- B. Decreases
- C. May increase or decrease; depends on the substance
- D. Remains unchanged
Explanation: For a pure substance, the triple point is a fixed combination of temperature and pressure at which all three phases coexist.
Correct answer: Remains unchanged- A. Isobaric
- B. Isochoric
- C. Adiabatic
- D. Isothermal
Explanation: The water is heated while the surrounding atmospheric pressure remains essentially constant, so the process is isobaric.
Correct answer: Isobaric- A. Pressure
- B. All (A), B. and (C)
- C. Temperature
- D. Composition
Explanation: An activity coefficient can vary with temperature, pressure, and mixture composition.
Correct answer: All (A), B. and (C)- A. Does not need the addition of external work for its functioning
- B. Transfers heat from high temperature to low temperature
- C. Accomplishes the reverse effect of the heat engine
- D. None of these
Explanation: A refrigerator operates as the reverse of a heat engine: it uses work to transfer heat from a low-temperature region to a high-temperature…
Correct answer: Accomplishes the reverse effect of the heat engine- A. Margules
- B. Van Laar
- C. Gibbs-Helmholtz
- D. Gibbs-Duhem
Explanation: The Gibbs-Duhem equation relates changes in component chemical potentials or fugacities to composition at constant temperature and…
Correct answer: Gibbs-Duhem- A. The chemical potential of each component should be same in the two phases
- B. The temperature of each phase should be same
- C. The pressure should be same in the two phases
- D. The concentration of each component should be same in the two phases
Explanation: Phase equilibrium requires the chemical potential of every component to be equal in the coexisting phases, along with common thermal and…
Correct answer: The chemical potential of each component should be same in the two phases- A. Activity
- B. Activity co-efficient
- C. Fugacity
- D. Fugacity co-efficient
Explanation: For an ideal liquid solution, each component obeys Raoult's-law behaviour, so its activity coefficient is unity.
Correct answer: Activity co-efficient- A. Adiabatic
- B. Polytropic
- C. Constant volume
- D. Constant pressure
Explanation: For a closed system with only pressure-volume work, the first law gives δQ = dU + P dV.
Correct answer: Constant volume- A. RT d ln f
- B. RT d ln P
- C. R d ln f
- D. None of these
Explanation: For a real gas, fugacity replaces pressure in the chemical-potential relation: dμ = RT d ln f at constant temperature.
Correct answer: RT d ln f