Free Chemical Engineering Thermodynamics MCQs with Answers

• A. Zeroth
• B. Second
• C. First
• D. Third

Explanation: A refrigerator transfers heat from a low-temperature region to a high-temperature region, which cannot occur spontaneously and requires…

• A. Independent of pressure
• B. Independent of temperature
• C. Zero at absolute zero temperature for a perfect crystalline substance
• D. All A, B. & C

Explanation: The third law states that the entropy of a perfect crystalline substance approaches zero as temperature approaches absolute zero.

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

Explanation: For a pure substance, the chemical potential equals its molar Gibbs free energy.

• A. Gibbs free energy
• B. Entropy
• C. Internal energy
• D. All (A), B. & (C)

Explanation: At the phase-transition temperature and pressure, the two phases have equal chemical potential, so the Gibbs free energy does not change…

• A. Isothermal
• B. Adiabatic
• C. Isometric
• D. None of these

Explanation: Sound propagation is rapid enough that there is essentially no time for heat transfer between the compressed air and its surroundings.

• A. Prandtl number
• B. Mach number
• C. Weber number
• D. Adiabatic constant

Explanation: The ratio of heat capacities, Cp/Cv, is denoted by gamma and is called the adiabatic index or adiabatic constant.

• A. Increases
• B. Increases linearly
• C. Decreases
• D. Remain constant

Explanation: Heating a liquid increases the average molecular energy, allowing more molecules to escape into the vapour phase, so vapour pressure…

• A. Reduce the cost of compressor
• B. Resemble closely to isothermal compression
• C. Reduce the size requirement
• D. Are easy to control

Explanation: Interstage cooling lowers the gas temperature and reduces the work required, so multistage compression approaches isothermal compression…

• A. pv = constant
• B. pvr= constant
• C. pvr = constant, and process is reversible
• D. None of these

Explanation: An isentropic process has constant entropy and is reversible and adiabatic; for an ideal gas it satisfies pV^gamma = constant.

• A. Is always negative
• B. Is equal to the heat of formation
• C. Can't be known without calculating it
• D. Is always positive

Explanation: With the thermodynamic sign convention, combustion is exothermic, so its enthalpy change or heat of reaction is negative.

• A. GCV at constant volume
• B. GCV at constant pressure
• C. NCV at constant pressure
• D. NCV at constant volume

Explanation: A bomb calorimeter operates at constant volume, and the heat measured corresponds to the gross calorific value because the water formed…

• A. Minimise its corrosion
• B. Avoid radiation heat loss
• C. Make it look attractive
• D. None of these

Explanation: A polished, silvery surface has low emissivity, so it radiates and absorbs less heat.

• A. Molten sodium cooled
• B. CO2 gas cooled
• C. Boiling water
• D. Pressurised water

Explanation: A boiling-water reactor produces steam directly in the reactor, avoiding the separate steam generator and reducing intermediate…

• A. CO2
• B. NO2
• C. NO
• D. O2

Explanation: Oxygen has two unpaired electrons in its molecular orbitals, giving it stronger paramagnetism than NO and NO₂, which each have one…

• A. Defined on the basis of melting point of ice and evaporation temperature of water vapor
• B. Both B. and C.
• C. Having an interval of 100° between ice point to steam point
• D. Defined on the basis of melting point of ice and condensation temperature of water vapor

Explanation: The Celsius scale assigns 0°C to the ice point and 100°C to the steam point, giving an interval of 100 degrees.

• A. Mercury thermometer
• B. Dilatometer
• C. Beckman thermometer
• D. Bimetallic thermometer

Explanation: A Beckmann thermometer is designed to detect very small temperature differences, making it suitable for measuring freezing-point…

• A. None of these
• B. Nitrogen
• C. Hydrogen
• D. Helium

Explanation: Helium is preferred for sub-zero gas thermometry because it remains gaseous at much lower temperatures and behaves nearly ideally over a…

• A. 32°R
• B. 273°K
• C. 492°R
• D. 32°F

Explanation: The triple point of water is approximately 273.16 K, 491.7°R, and 32.01°F, so 273 K, 492°R, and 32°F are rounded representations.

• A. 1 atm
• B. 1 kgf/cm2
• C. 0.98 Pascal
• D. 10 torr

Explanation: Here ata denotes a technical atmosphere absolute, equal to 1 kgf/cm² absolute and approximately 0.98 standard atm.

• A. Independent of temperature
• B. Unchanged with pressure changes
• C. Increased with decrease in pressure
• D. Increases with rise in pressure

Explanation: A negative volume change on mixing means pressure favors the mixed solution, increasing the amount that can dissolve.