421. Efficiency of a Carnot engine working between temperatures T₁ and T₂ (T₁ < T₂) is
A. (T₂ – T₁)/T₂
B. (T₂ – T₁)/T₁
C. (T₁ – T₂)/T₂
D. (T₁ – T₂)/T₁
✅ The correct answer is option A.
Thermodynamics MCQs
422. In case of the decomposition of hydroiodic acid (2HI ⇋ H₂ + I₂), addition of H₂ (at equilibrium condition) will
A. Increase the partial pressure of I₂
B. Decrease the partial pressure of HI
C. Diminish the degree of dissociation of HI
D. None of these
✅ The correct answer is option C.
423. In the equation, PVn = constant, if the value of n is in between 1 and y (i.e. Cp/Cv), then it represents a reversible __________ process.
A. Isometric
B. Polytropic
C. Isentropic
D. Isobaric
✅ The correct answer is option B.
424. At triple point (for one component system), vapour pressure of solid as compared to that of liquid will be
A. More
B. Less
C. Same
D. More or less ; depending on the system
✅ The correct answer is option C.
425. High __________ is an undesirable property for a good refrigerant.
A. Specific heat
B. Latent heat of vaporisation
C. Viscosity
D. Specific vapor volume
✅ The correct answer is option C.
426. For spontaneous changes in an isolated system (S = entropy)
A. Ds = 0
B. Ds <0
C. Ds > 0
D. Ds = Constant
✅ The correct answer is option C.
427. For a stable phase at constant pressure and temperature, the fugacity of each component in a binary system __________ as its mole fraction increases.
A. Decreases
B. Increases
C. Remains same
D. Decreases linearly
✅ The correct answer is option B.
428. As the time is passing, entropy of the universe
A. Is increasing
B. Is decreasing
C. Remains constant
D. Data insufficient, can’t be predicted
✅ The correct answer is option A.
429. In a P-V diagram (for an ideal gas), an isothermal curve will coincide withan adiabatic curve (through a point), when
A. Cp < Cv
B. Cp = Cv
C. Cp > Cv
D. Cp ≥ Cv
✅ The correct answer is option B.
430. The first law of thermodynamics is a statement of conservation of
A. Heat
B. Momentum
C. Energy
D. Work
✅ The correct answer is option C.