21. Which of the following equations is obtained on combining 1st and 2nd law of thermodynamics, for a system of constant mass?
A. DE = Tds – PdV
B. DQ = CvdT + PdV
C. DQ = CpdT + Vdp
D. Tds = dE – PdV
✅ The correct answer is option A.
Thermodynamics MCQs
22. The necessary condition for phase equilibrium in a multiphase system of N components is that the
A. Chemical potentials of a given component should be equal in all phases
B. Chemical potentials of all components should be same in a particular phase
C. Sum of the chemical potentials of any given component in all the phases should be the same
D. None of these
✅ The correct answer is option A.
23. No work is done by the system, when a reaction occurs at constant
A. Volume
B. Temperature
C. Pressure
D. None of these
✅ The correct answer is option A.
24. A gas performs the maximum work, when it expands
A. Non-uniformly
B. Adiabatically
C. Isobarically
D. Isothermally
✅ The correct answer is option C.
25. The kinetic energy of gas molecule is zero at
A. 0°C
B. 273°C
C. 100°C
D. -273°C
✅ The correct answer is option D.
26. One ton of refrigeration is defined as the heat rate corresponding to melting of one ton of ice in one
A. Hour
B. Day
C. Minute
D. Second
✅ The correct answer is option B.
27. There is a change in __________ during the phase transition.
A. Volume
B. Pressure
C. Temperature
D. All of the above
✅ The correct answer is option A.
28. The compressibility factor of a gas is given by (where, V₁ = actual volume of the gas V₂ = gas volume predicted by ideal gas law )
A. V₁/V₂
B. V₂/V₁
C. V₁-V₂
D. V₁.V₂
✅ The correct answer is option A.
29. Choose the condition that must be specified in order to liquify CO₂ (triple point for CO₂ is – 57°C and 5.2 atm).
A. Pressure must be kept below 5.2 atm
B. Temperature must be kept above – 57°C
C. Pressure must be kept below 5.2 atm. and temperature must be kept above 57°C
D. Pressure and temperature must be kept below 5.2 atm. and – 57°C respectively
✅ The correct answer is option D.
30. For an ideal liquid solution, which of the following is unity?
A. Activity
B. Fugacity
C. Activity co-efficient
D. Fugacity co-efficient
✅ The correct answer is option C.