81. Third law of thermodynamics is concerned with the
A. Value of absolute entropy
B. Energy transfer
C. Direction of energy transfer
D. None of these
✅ The correct answer is option A.
Thermodynamics MCQs
82. Lenz’s law results from the law of conservation of
A. Mass
B. Momentum
C. Energy
D. None of these
✅ The correct answer is option C.
83. Isotherm on an enthalpy-concentration diagram, for an ideal solution will be a
A. Straight line
B. Sine curve
C. Parabola
D. Hyperbola
✅ The correct answer is option A.
84. Ideal refrigeration cycle 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
✅ The correct answer is option B.
85. Which of the following exemplifies an adiabatic process?
A. Melting of ice
B. Condensation of alcohol vapor
C. Sudden bursting of a cycle tube
D. Evaporation of water
✅ The correct answer is option C.
86. A system in which there is exchange of energy but not of mass, is called a/an __________ system.
A. Isolated
B. Open
C. Insulated
D. Closed
✅ The correct answer is option D.
87. Sound waves propagation in air exemplifies an __________ process.
A. Adiabatic
B. Isothermal
C. Isometric
D. None of these
✅ The correct answer is option A.
88. Entropy of the system decreases, when
A. Snow melts into water
B. A gas expands spontaneously from high pressure to low pressure
C. Water is converted into ice
D. Both B & C
✅ The correct answer is option D.
89. In an ideal gas mixture, fugacity of a species is equal to its
A. Vapor pressure
B. Partial pressure
C. Chemical potential
D. None of these
✅ The correct answer is option B.
90. What is the degree of freedom for two mis-cible (non-reacting) substances in vapor-liquid equilibrium forming an azeotrope?
A. 0
B. 1
C. 2
D. 3
✅ The correct answer is option C.