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 6 of 30
101. Near their critical temperatures, all gases occupy volumes _____________ that of the ideal gas?
- A. Half
- B. Same as
- C. More than
- D. Less than
Explanation: Near the critical temperature, attractive intermolecular forces make a real gas more compressible than an ideal gas, so its volume at the…
Correct answer: Less than102. The number of degrees of freedom for a mixture of ice and water (liquid) are ____________________?
- A. 3
- B. 2
- C. 1
- D. 0
Explanation: Gibbs phase rule gives F = C - P + 2 = 1 - 2 + 2 = 1 for a one-component ice-water system.
Correct answer: 1- A. Saturated vapour
- B. Gas
- C. Solid
- D. Liquid
Explanation: Above the critical temperature, no amount of pressure can produce a separate liquid-vapour phase transition.
Correct answer: Gas- A. Vapour pressure is relatively low and the temperature does not vary over wide limits
- B. Vapour obeys the ideal gas law and the latent heat of vaporisation is constant
- C. Volume in the liquid state is negligible compared with that in the vapour state
- D. All A, B. and C
Explanation: The usual Clausius-Clapeyron approximation assumes an ideal-gas vapour, negligible liquid volume, nearly constant latent heat, and a…
Correct answer: All A, B. and C- A. 0
- B. ∞
- C. -ve
- D. +ve
Explanation: For an ideal gas, κT = 1/P whereas κS = 1/(γP), with γ greater than one.
Correct answer: +ve- A. Adiabatic
- B. Isothermal
- C. Reversible
- D. None of these
Explanation: For an ideal gas, PV = nRT, so PV remaining constant means the temperature is constant.
Correct answer: Isothermal- A. dQ = CpdT + Vdp
- B. dQ = CvdT + PdV
- C. dE = Tds - PdV
- D. Tds = dE - PdV
Explanation: Combining the first and second laws for a closed, simple compressible system gives dE = Tds - PdV.
Correct answer: dE = Tds - PdV- A. Pressure
- B. Volume
- C. All A, B. & C
- D. Temperature
Explanation: For the equation P(V - b) = RT, the volume-dependent terms cancel in (∂U/∂V)T = T(∂P/∂T)V - P, giving zero.
Correct answer: Temperature- A. 100
- B. 50
- C. 205
- D. 200
Explanation: At constant temperature, Boyle's law gives P1V1 = P2V2. Halving the pressure therefore doubles the volume: 100 × 2 = 200 cc.
Correct answer: 200110. All gases above its inversion temperature, in a throttling process will show__________________?
- A. No change in temperature
- B. A heating effect
- C. A cooling effect
- D. Either A. or (C)
Explanation: Above the inversion temperature, the Joule-Thomson coefficient is negative, so a pressure drop during throttling causes the gas…
Correct answer: A heating effect- A. May increase or decrease; depends on the substance
- B. Decreases
- C. Remains unchanged
- D. Increases
Explanation: The temperature dependence of internal energy is governed by heat capacity, dU = Cv dT at constant volume, and Cv is normally positive.
Correct answer: Increases- A. None of these
- B. Entropy change
- C. Gibbs free energy
- D. CV
Explanation: By definition, the isobaric heat capacity is Cp = (∂H/∂T)P. Since Cp is not among the listed choices, none of these is correct.
Correct answer: None of these- A. R log10 4
- B. R loge 4
- C. Cv log10 4
- D. Cv loge 4
Explanation: For an ideal gas in a reversible isothermal process, ΔS = R ln(V2/V1). With V2/V1 = 4, the change is R loge 4.
Correct answer: R loge 4- A. Non-solidifiable
- B. Saturated
- C. Sub-cooled
- D. None of these
Explanation: At a specified temperature, a liquid whose pressure exceeds its vapour pressure is below its saturation condition.
Correct answer: Sub-cooled115. The first law of thermodynamics is a restatement of the law of conservation of_________________?
- A. Mass
- B. None of these
- C. Momentum
- D. Energy
Explanation: The first law applies conservation of energy to a thermodynamic system, accounting for heat, work, and changes in stored energy.
Correct answer: Energy- A. Pressure
- B. Temperature
- C. Enthalpy
- D. Entropy
Explanation: A throttling valve is adiabatic and does no shaft work, so enthalpy remains constant; for a perfect gas, this also means temperature…
Correct answer: Pressure117. Co-efficient of Performance (COP) of a refrigerator is the ratio of the ______________________?
- A. Work required to refrigeration obtained
- B. Refrigeration obtained to the work required
- C. Lower to higher temperature
- D. Higher to lower temperature
Explanation: Refrigerator performance is measured by the cooling effect obtained divided by the work supplied: COP = refrigeration effect / work input.
Correct answer: Refrigeration obtained to the work required- A. At constant pressure
- B. By throttling
- C. By expansion in an engine
- D. None of these
Explanation: The Claude process produces cooling mainly by allowing gas to expand in an engine, where it performs work and falls in temperature.
Correct answer: By expansion in an engine- A. One fourth of its original value
- B. Doubled
- C. Halved
- D. Same
Explanation: The equilibrium constant depends on temperature, not on the instantaneous concentrations.
Correct answer: Same- A. More than
- B. Equal to
- C. Less than
- D. Data insufficient, can't be predicted
Explanation: For an ideal gas, fugacity equals pressure, and activity is fugacity divided by the standard-state fugacity.
Correct answer: Equal to