Free Chemical Engineering Thermodynamics MCQs with Answers

• A. - ve
• B. ∞
• C. + ve
• D. 0

Explanation: Mixing stable, unlike components at constant temperature and pressure lowers Gibbs free energy, so ΔGmix is negative.

• A. Pressure
• B. Composition
• C. All (A), B. and (C)
• D. Temperature

Explanation: A component's fugacity in a solution is determined by its chemical potential, which varies with temperature, pressure, and composition.

• A. Pressure
• B. Molal heat capacity
• C. Heat capacity
• D. Concentration

Explanation: Heat capacity scales with the amount of material, making it an extensive property.

• A. Isobaric
• B. Isothermal
• C. Isentropic
• D. Isometric

Explanation: With PV^n constant and n = 0, the relation becomes P = constant. A constant-pressure process is isobaric, represented by option (a).

• A. 1
• B. < 1
• C. > 1
• D. >> 1

Explanation: Adiabatic compressibility is smaller than isothermal compressibility because temperature cannot remain constant during adiabatic…

• A. 300 × (32/7)
• B. 300 × (33/5)
• C. 300 × (333/7)
• D. 300 × (35/7)

Explanation: For reversible adiabatic compression, T₂/T₁ = (P₂/P₁)^((γ−1)/γ) = 3^(2/7), since γ = 7/5. Thus T₂ = 300 × 3^(2/7), represented by option a.

• A. Air compressor
• B. None of these
• C. Boiler
• D. Liquid cooling system of an automobile

Explanation: An automobile's liquid cooling system normally circulates a fixed quantity of coolant within a closed loop, so no mass crosses the system…

• A. End states only
• B. Initial state only
• C. Rate of heat transmission
• D. None of these

Explanation: For an adiabatic closed system, Q = 0, so the work is determined by the change in internal energy, W = U₁ − U₂ under the usual sign…

• A. Increases with rise in pressure
• B. Decreases with rise in pressure
• C. Is independent of pressure
• D. Is a path function

Explanation: For an ideal gas, enthalpy depends only on temperature, not on pressure, because intermolecular effects are absent.

• A. Temperature dependence of heat of phase transition
• B. Effect of an inert gas on vapour pressure
• C. Calculation of ΔF for spontaneous phase change
• D. Rate of change of vapour pressure with temperature

Explanation: The Clapeyron equation relates the slope of a phase-equilibrium curve to temperature, commonly expressed as the rate of change of…

• A. Value of absolute entropy
• B. Energy transfer
• C. Direction of energy transfer
• D. None of these

Explanation: The third law provides a reference for assigning absolute entropy, stating that the entropy of a perfect crystal approaches zero as…

• A. In standard state
• B. In ideal state
• C. At low temperature
• D. At high pressure

Explanation: For an ideal gas, the fugacity coefficient is unity, so fugacity is numerically equal to pressure.

• A. Vapour pressure of liquid
• B. Departure of gas phase from ideal gas law
• C. Departure from ideal solution behaviour
• D. None of these

Explanation: The activity coefficient compares a component's actual activity with its ideal-solution value, so it measures departure from ideal…

• A. Volume
• B. Enthalpy
• C. Neither A. nor B
• D. Both A. & B

Explanation: An ideal solution has zero enthalpy and zero volume change on mixing, although its entropy of mixing is positive.

• A. Ideal
• B. Very high pressure
• C. Very low temperature
• D. All of the above

Explanation: The relation Cp minus Cv equals R follows from the ideal-gas equation of state and applies to ideal gases.

• A. d ln p/dt = RT2/Hvap
• B. d ln p/dt = Hvap/RT2
• C. dp/dt = RT2/Hvap
• D. dp/dt = Hvap/RT2

Explanation: With liquid molar volume negligible and the vapour treated as ideal, the Clausius-Clapeyron equation becomes d ln p/dT = Hvap/(R T²).

• A. Positive
• B. Negative
• C. Zero
• D. Infinity

Explanation: Over a complete ideal refrigeration cycle, the working fluid returns to its initial state, and internal energy is a state function.

• A. All require same work
• B. Isothermal process
• C. Isobaric process
• D. Adiabatic process

Explanation: For compression from the same initial to final volume, a reversible adiabatic path has a higher pressure than an isothermal path, so the…

• A. Mole fraction
• B. Fugacity at the same temperature and pressure
• C. Partial pressure
• D. None of these

Explanation: For an ideal solution, Raoult's-law behaviour gives the activity of component i as its mole fraction, ai = xi.

• A. 0
• B. 1
• C. 2
• D. 3

Explanation: Applying the phase rule, F = C − P + 2 = 1 − 2 + 2 = 1. Thus, fixing either temperature or pressure fixes the other along the…