Free Chemical Engineering Thermodynamics MCQs with Answers

• A. 100.67
• B. 10-0.67
• C. 10-3.01
• D. 103.01

Explanation: Subtracting the second reaction from the first gives CO + H₂O → CO₂ + H₂, so the equilibrium constants divide: K_P = 10^1.84/10^1.17 =…

• A. Depends on the pressure only
• B. Is independent of the mechanism of reaction
• C. Depends on both pressure and mechanism of reaction
• D. Depends on the mechanism of reaction only

Explanation: The heat of reaction is a state-function difference between products and reactants, so it does not depend on the reaction mechanism or the…

• A. Temperature and pressure
• B. Pressure only
• C. Temperature only
• D. Ratio of reactants

Explanation: For a specified reaction, the equilibrium constant changes with temperature through the standard Gibbs-energy relation.

• A. 2O3 ⇌ 3O2
• B. 2SO2 + O2 ⇌ 2SO3
• C. 2NO2 ⇌ N2O4
• D. N2 + O2 ⇌ 2NO

Explanation: Pressure has no effect on gas-phase equilibrium when the total gaseous mole number is unchanged.

• A. No change
• B. Increase
• C. Decrease
• D. Unpredictable from the data

Explanation: For CaCO₃(s) ⇌ CaO(s) + CO₂(g), the pure-solid activities remain essentially unity.

• A. Water will evaporate
• B. Equilibrium will not be attained
• C. More water will be formed
• D. More ice will be formed

Explanation: Water is denser than ice, so increasing pressure favors the phase occupying less volume, namely liquid water.

• A. Unpredictable
• B. More
• C. Same
• D. Less

Explanation: At the same temperature, pressure, and volume, water vapour replaces part of the dry air and has a lower molecular mass than air.

• A. Escaping tendency of each component from the liquid phase to the vapor phase is exactly
• B. All A., B. and C.
• C. Temperature of the liquid phase is equal to that of the vapor phase
• D. Total pressure throughout the liquid phase is equal to that throughout the vapor phase
• E. equal to that from vapor phase to liquid phase

Explanation: Physical equilibrium requires equal temperature and equal escaping tendency, or chemical potential, for each component in the two phases.

• A. a1 = a2
• B. None of these
• C. a1 = 0.5 a2
• D. a1 = 2a2

Explanation: Relative volatility depends on the vapour-liquid equilibrium and generally changes with pressure and temperature, but its change between 1…

• A. Less than the sum of the vapour pressure of the components
• B. Less than that computed for ideality
• C. Greater than that computed for ideality
• D. None of these

Explanation: Positive deviation means the unlike-molecule attractions are weaker than those in the pure liquids, allowing more molecules to escape into…

• A. Boiling point
• B. Freezing point
• C. Vapour pressure
• D. Both B. and C.

Explanation: A dissolved nonvolatile solute lowers the solvent’s vapour pressure and consequently lowers the freezing point, while raising the boiling…

• A. Solvents
• B. Non-ideal solution only
• C. Non-volatile solute
• D. All liquid solutions

Explanation: Raoult's law relates the partial pressure of a volatile component to its liquid-phase mole fraction and is normally applied to the solvent…

• A. 35% solution of NH3 in water
• B. 35% solution of camphor in water
• C. A solution of benzene, toluene and o-xylene
• D. A solution of polar organic compounds (not of homologue of a series)

Explanation: Benzene, toluene, and o-xylene are similar, nonpolar members of a homologous aromatic series, so their intermolecular interactions are…

• A. The mixture contain optical isomers
• B. The composition of the mixture, in percent by volume is: o-xylene 30, p-xylene 60. and mxylene
• C. 10
• D. The composition of the mixture in mole percent is: o-xylene 30, p-xylene 60 and m-xyoene 10
• E. The mixture exhibits an azeotrope at 101.3 kPa

Explanation: The stated weight percentages cannot also be the volume or mole percentages because the three xylene isomers have different molecular and…

• A. Water-hydrochloric acid
• B. Acetone-carbon disulphide
• C. Water-ethyl alcohol
• D. n-heptane-n-octane

Explanation: A water-hydrochloric acid mixture forms a maximum-boiling azeotrope because its boiling temperature is higher than that of either pure…

• A. Real solutions
• B. Ideal solutions
• C. Mixture of water and alcohol
• D. Non-ideal gases

Explanation: Raoult's law is strictly applicable to ideal liquid solutions, where each component's partial pressure equals its mole fraction multiplied…

• A. Benzene-toluene
• B. Hydrochloric acid-water
• C. Ethyl alcohol-water
• D. All A., B. and C.

Explanation: Ethanol and water form a minimum-boiling azeotrope at approximately atmospheric pressure because their vapour-liquid equilibrium shows…

• A. Decreasing pressure
• B. Increasing temperature
• C. Increasing pressure
• D. No means

Explanation: The ethanol-water azeotrope can be removed by reducing pressure sufficiently, because azeotropic composition depends on pressure.

• A. Inversely
• B. Linearly
• C. Exponentially
• D. None of these

Explanation: For an ideal solution, Raoult's law gives total pressure as the sum of each component's vapour pressure contribution, so it varies…

• A. Size of component molecules are not equal
• B. Attractive forces between like and unlike molecules in the solution are approximately equal
• C. Chemical combination or molecular association between unlike molecules takes place in the
• D. Component molecules are non-polar
• E. formation of solution

Explanation: Non-polar components with similar molecular size and comparable intermolecular forces tend to form nearly ideal solutions, so Raoult's law…