Free Chemical Engineering Thermodynamics MCQs with Answers

• A. None of these
• B. The physical state (e.g., solid, liquid or gaseous) of reactants and products
• C. Whether the reaction is carried out at constant temperature or constant pressure
• D. The route/method through which final products are obtained

Explanation: Enthalpy is a state function, so the heat of reaction is independent of the route or sequence used to obtain the products, which is Hess's…

• A. Boyle's temperature
• B. Triple point
• C. Eutectic point
• D. Inversion temperature

Explanation: Boyle’s temperature is the temperature at which the first correction to ideal-gas behaviour vanishes, so the gas obeys Boyle’s law over…

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

Explanation: For an ideal gas, internal energy is a function of temperature only, not of pressure or volume separately.

• A. Independent of the temperature
• B. Increased with the increase in pressure
• C. Unchanged by the pressure change
• D. Decreased with the increase in pressure

Explanation: When mixing causes volume expansion, increasing pressure favours the lower-volume state and reduces dissolution.

• A. Both B. & C.
• B. Decreases with increasing pressure
• C. Becomes zero at the critical point
• D. Increases with pressure rise

Explanation: The heat of vaporisation decreases as pressure rises because the liquid and vapour become more similar near the critical point.

• A. Vapor to liquid
• B. One allotropic form to another allotropic form
• C. Solid to liquid
• D. Vapor to solid

Explanation: Heat of transition refers to the heat absorbed or released when a substance changes between two allotropic forms, such as one crystal…

• A. 100 N/m2
• B. 760 mm wc
• C. 13.6 cms of Hg
• D. 76 cms of Hg

Explanation: At 100°C, water boils at standard atmospheric pressure, whose pressure is 760 mm Hg or 76 cm Hg. Therefore, the 76 cm Hg option is correct.

• A. Absolute temperature is a measure of the kinetic energy of molecules
• B. Molecules possess appreciable volume
• C. Energy is lost during molecular collisions
• D. None of these

Explanation: Kinetic theory relates absolute temperature to the average translational kinetic energy of gas molecules.

• A. The strong base and strong acid reacts completely
• B. The salt formed does not hydrolyse
• C. Only OH- and H+ ions react in every case
• D. The strong base and strong acid reacts in aqueous solution

Explanation: For a strong acid and strong base, both electrolytes ionise completely, so the net reaction is always H+ + OH− → H2O.

• A. 57.46
• B. -57.46
• C. 114.92
• D. -28.73

Explanation: Neutralisation of H+ and OH− releases 57.46 kJ per kg-mole of water formed.

• A. Boyle's law
• B. Amagat's law
• C. Raoult's law
• D. Trouton's rule

Explanation: An ideal solution obeys Raoult’s law across the entire composition range because each component’s partial pressure equals its mole…

• A. -109.5
• B. +109.5
• C. +180
• D. +100

Explanation: By Hess’s law, formation of CO can be obtained by subtracting CO combustion from carbon combustion: −394 − (−284.5) = −109.5 kJ/kg-mole.

• A. Equation of state
• B. Gibbs Duhem equation
• C. Ideal gas equation
• D. None of these

Explanation: An equation of state is the general relation connecting pressure, volume, temperature and composition of a substance.

• A. More
• B. Less
• C. Same
• D. More or less; depending on the system

Explanation: At the triple point, solid, liquid and vapour coexist in equilibrium. The solid and liquid therefore have the same vapour pressure at that…

• A. Temperature vs. enthalpy
• B. Temperature vs. enthalpy
• C. Entropy vs. enthalpy
• D. Temperature vs. internal energy

Explanation: A Mollier diagram is the h-s chart, plotting specific enthalpy against specific entropy.

• A. Boyle
• B. Critical
• C. Inversion
• D. Reduced

Explanation: The Boyle temperature is the temperature at which the attractive and repulsive intermolecular effects nearly cancel, so a real gas follows…

• A. Isothermally
• B. Isobarically
• C. Adiabatically
• D. None of these

Explanation: A turbine is usually well insulated and has a short residence time, so heat transfer is negligible and the expansion is approximately…

• A. 0
• B. 1
• C. 2
• D. 3

Explanation: Gibbs phase rule gives F = C - P + 2 = 1 - 3 + 2 = 0 for water at the triple point.

• A. Equal to
• B. Less than
• C. More than
• D. Not related to

Explanation: Chemical potential is the molar Gibbs free energy, and for a pure substance it is also equal to that substance's partial molal Gibbs free…

• A. its internal energy (U) decreases and its entropy (S) increases
• B. U and S both decreases
• C. U decreases but S is constant
• D. U is constant but S decreases

Explanation: For reversible cooling, heat leaves the system, so entropy decreases because dS = δQrev/T is negative.