Free Chemical Engineering Thermodynamics MCQs with Answers

• A. Kelvin's
• B. Antoine's
• C. Kirchoff's
• D. None of these

Explanation: Kirchhoff's law relates the temperature dependence of the heat of reaction to the difference between the heat capacities of products and…

• A. Isothermal
• B. Reversible
• C. Adiabatic
• D. Irreversible

Explanation: Friction converts organized mechanical energy into heat and generates entropy, so the process cannot be reversed without leaving changes…

• A. Pressure
• B. Temperature
• C. Volume
• D. Molar concentration

Explanation: Fugacity is an effective pressure used to represent the escaping tendency of a real fluid, so it has the same dimensions and unit as…

• A. Gibbs-Duhem
• B. Clapeyron
• C. Maxwell's
• D. None of these

Explanation: The Clapeyron equation gives the slope of the phase-equilibrium curve, dP/dT, in terms of latent heat and the volume change between the…

• A. Is the analog of linear frictionless motion in machines
• B. Is an idealised visualisation of behaviour of a system
• C. Yields an amount of work less than that of a reversible process
• D. Yields the maximum amount of work

Explanation: For the same initial and final states in a work-producing process, irreversibility destroys some work potential, so the work obtained is…

• A. Same as Carnot cycle
• B. Same as reverse Carnot cycle
• C. Dependent on the refrigerant's properties
• D. The least efficient of all refrigeration processes

Explanation: An ideal refrigerator operates on the reversed Carnot cycle, because the Carnot cycle produces the maximum possible COP between two…

• A. Pressure
• B. Temperature
• C. Both A. & B
• D. Neither A. nor B

Explanation: For an incompressible substance, the pressure contribution to internal energy is negligible, giving approximately du = Cv dT.

• A. Does not depend upon temperature
• B. Is independent of pressure only
• C. Is independent of both pressure and volume
• D. Is independent of volume only

Explanation: For an ideal gas, internal energy and Cv depend primarily on temperature, while pressure and volume are not independent effects.

• A. Reversible and isothermal
• B. Reversible and constant enthalpy
• C. Reversible and constant entropy
• D. Irreversible and constant enthalpy

Explanation: In throttling, there is no appreciable work or heat transfer, so the steady-flow energy balance gives h1 = h2.

• A. Joule-Thompson co-efficient
• B. Specific heat at constant volume (Cv)
• C. Specific heat at constant pressure (Cp)
• D. None of these

Explanation: The Joule-Thomson coefficient is defined as μJT = (∂T/∂P)H, describing the temperature change with pressure during constant-enthalpy…

• A. Ammonia
• B. Water
• C. Freon
• D. Brine

Explanation: Jet or ejector refrigerators normally use water vapour as the motive and refrigerating fluid, especially in steam-jet systems.

• A. Conduction
• B. Convection
• C. Condensation
• D. Radiation

Explanation: The Gibbs phase rule applies to systems containing phases in equilibrium, such as liquid and vapour during condensation.

• A. Doubling the absolute temperature as well as pressure of the gas
• B. Reducing pressure to one fourth at constant temperature
• C. Reducing temperature to one fourth at constant pressure
• D. Reducing the temperature to half and doubling the pressure

Explanation: For a gas at constant temperature, V is inversely proportional to pressure, so reducing pressure to one-fourth makes the volume four times…

• A. Reduced pressure and reduced temperature
• B. Pressure and temperature
• C. Critical pressure and critical temperature
• D. None of these

Explanation: The principle of corresponding states states that gases show similar compressibility behaviour at equal reduced pressure and reduced…

• A. Δ H = 0 and ΔS = 0
• B. Δ H ≠ 0 and ΔS = 0
• C. Δ H ≠ 0 and ΔS ≠ 0
• D. Δ H = 0 and ΔS ≠ 0

Explanation: Adiabatic operation gives no heat transfer, while reversibility makes the entropy change zero.

• A. None of these
• B. Desuperheated
• C. Non-condensable
• D. Superheated

Explanation: At a given temperature, a vapour pressure below the saturation pressure indicates that the vapour is superheated.

• A. Energy
• B. Mass
• C. Momentum
• D. None of these

Explanation: The first law states that energy is conserved: it can change between heat, work, internal energy and other forms, but cannot be created or…

• A. Heat transfer from low temperature to high temperature source is not possible without external
• B. Heat capacity of a crystalline solid is zero at absolute zero temperature
• C. work
• D. Gases having same reduced properties behaves similarly
• E. None of these

Explanation: For a perfect crystalline solid, the heat capacity approaches zero as absolute zero is reached, which is the standard engineering form…

• A. (∂T/∂V)S = (∂p/∂S)V
• B. (∂T/∂P)S = (∂V/∂S)P
• C. (∂V/∂T)P = -(∂S/∂P)T
• D. (∂P/∂T)V = (∂S/∂V)T

Explanation: The Maxwell relation from dG = VdP − SdT is (∂V/∂T)P = −(∂S/∂P)T. This relation provides a consistency check for tabulated…

• A. Increased or decreased COP; depending upon the type of refrigerant
• B. Decreased COP
• C. No change in the value of COP
• D. Enhanced COP

Explanation: Raising the evaporator temperature increases the refrigeration effect and usually reduces the compressor pressure ratio and work…