Thermodynamics MCQs Archives

171. It is desired to bring about a certain change in the state of a system by performing work on the system under adiabatic conditions.

A. The amount of work needed is path dependent

B. Work alone can not bring out such a change of state

C. The amount of work needed is independent of path

D. More information is needed to conclude anything about the path dependence or otherwise of the work needed

✅ The correct answer is option A.

172. At 60° C, vapour pressure of methanol and water are 84.562 kPa and 19.953 kPa respectively. An aqueous solution of methanol at 60° C exerts a pressure of 39.223 kPa; the liquid phase and vapour phase mole fractions of methanol are 0.1686 and 0.5714 respectively. Activity co-efficient of methanol is

A. 1.572

B. 1.9398

C. 3.389

D. 4.238

✅ The correct answer is option A.

173. If the vapour pressure at two temperatures of a solid phase in equilibrium with its liquid phase are known, then the latent heat of fusion can be calculated by the

A. Maxwell’s equation

B. Clayperon-Claussius equation

C. Van Laar equation

D. Nernst Heat Theorem

✅ The correct answer is option B.

174. 4 kg moles of an ideal gas expands in vacuum spontaneously. The work done is

A. 4 J

B. ∞

C. 0

D. 8 J

✅ The correct answer is option C.

175. The reaction A (l) R(g) is allowed to reach equilibrium conditions in an autoclave. At equilibrium, there are two phases, one a pure liquid phase of A and the other a vapor phase of A, R and S. Initially A alone is present. The number of degrees of freedom are

A. 1

B. 2

C. 3

D. 0

✅ The correct answer is option B.

176. A liquid under pressure greater than its vapour pressure for the temperature involved is called a __________ liquid.

A. Subcooled

B. Saturated

C. Non-solidifiable

D. None of these

✅ The correct answer is option A.

177. On a P-V diagram of an ideal gas, suppose a reversible adiabatic line intersects a reversible isothermal line at point A. Then at a point A, the slope of the reversible adiabatic line (∂P/∂V)S and the slope of the reversible isothermal line (∂P/∂V)T are related as (where, y = Cp/Cv) )

A. (∂P/∂V)S = (∂P/∂V)T

B. (∂P/∂V)S = [(∂P/∂V)T]Y

C. (∂P/∂V)S = y(∂P/∂V)T

D. (∂P/∂V)S = 1/y(∂P/∂V)T

✅ The correct answer is option C.

178. An ideal liquid refrigerant should

A. Not have a subatmospheric vapour pressure at the temperature in the refrigerator coils

B. Not have unduly high vapour pressure at the condenser temperature

C. Both A and B

D. Have low specific heat

✅ The correct answer is option C.

179. Fugacity and pressure are numerically equal, when the gas is

A. In standard state

B. At high pressure

C. At low temperature

D. In ideal state

✅ The correct answer is option D.

180. Compressibility factor (i.e., the ratio of actual volume of gas to the volume predicted by ideal gas law) for all gases are

A. Always greater than one

B. Same at the same reduced temperature

C. Same at the same reduced pressure

D. Both B & C

✅ The correct answer is option D.