121. At the critical point of a substance
A. The surface tension vanishes
B. Liquid and vapour have the same density
C. There is no distinction between liquid and vapour phases
D. All of the above
✅ The correct answer is option D.
Thermodynamics MCQs
122. A gas shows deviation from ideal behaviour at
A. Low pressure and high temperature
B. Low pressure and low temperature
C. Low temperature and high pressure
D. High temperature and high pressure
✅ The correct answer is option C.
123. At constant temperature and pressure, for one mole of a pure substance, the ratio of the free energy to the chemical potential is
A. Zero
B. One
C. Infinity
D. Negative
✅ The correct answer is option B.
124. Internal energy is equal to the heat absorbed in case of a/an __________ process.
A. Constant volume
B. Polytropic
C. Adiabatic
D. Constant pressure
✅ The correct answer is option A.
125. The expression, nCv(T₂ – T₁), is for the __________ of an ideal gas.
A. Work done under adiabatic condition
B. Co-efficient of thermal expansion
C. Compressibility
D. None of these
✅ The correct answer is option A.
126. At absolute zero temperature, all substances have the same
A. Heat capacity
B. Crystalline structure
C. Entropy
D. None of these
✅ The correct answer is option A.
127. Near their critical temperatures, all gases occupy volumes __________ that of the ideal gas.
A. Less than
B. Same as
C. More than
D. Half
✅ The correct answer is option A.
128. Which of the following is not affected by temperature changes?
A. Fugacity
B. Activity co-efficient
C. Free energy
D. None of these
✅ The correct answer is option D.
129. The theoretical minimum work required to separate one mole of a liquid mixture at 1 atm, containing 50 mole % each of n- heptane and n- octane into pure compounds each at 1 atm is
A. -2 RT ln 0.5
B. -RT ln 0.5
C. 0.5 RT
D. 2 RT
✅ The correct answer is option B.
130. The quantitative effect of temperature on chemical equilibrium is given by the
A. Vant-Hoff equation
B. Le-Chatelier’s principle
C. Arhenius equation
D. None of these
✅ The correct answer is option A.