Chemical Engineering Thermodynamics - Study Mode

[#296] A liquid under pressure greater than its vapour pressure for the temperature involved is called a __________ liquid.
Correct Answer

(A) Subcooled

Explanation

Solution: A subcooled liquid is at that state where if you want to vapourise the liquid at constant temperature we have to decrease the pressure hence we can say the liquid is at higher pressure under subcooled state.

[#297] Vapour which is at a pressure smaller than the saturation pressure for the temperature involved is called a __________ vapour.
Correct Answer

(A) Superheated

Explanation

Solution: . A superheated liquid is at that state where if you want to vapourise the liquid at constant temperature we have to increase the pressure hence we can say the liquid is at lower pressure under subcooled state.

[#298] The expression, nRT In $$frac{{{{ ext{P}}_1}}}{{{{ ext{P}}_2}}}$$, is for the ____ of an ideal gas.
Correct Answer

(C) Work done under isothermal condition

Explanation

Solution: Since, the expansion work is equal to $$delta w = PdV$$ Since for an ideal gas $$eqalign{
& PV = nRT cr
& Rightarrow w = int {frac{{nRT}}{V}} dV cr
& Rightarrow w = nRTln left( {frac{{{P_1}}}{{{P_2}}}}
ight) cr} $$ (hence for an ideal gas under isothermal conditions)

[#299] In a reversible process
Correct Answer

(A) Tds = dE + dW

Explanation

Solution: From second law of thermodynamics : $$eqalign{
& TdS geqslant delta Q cr
& Rightarrow TdS geqslant dU + delta W cr} $$ For an irreversible process $$TdS - dU - delta W > 0$$ And for an reversible process $$TdS - dU - delta W = 0$$

[#300] The kinetic energy of gas molecule is zero at
Correct Answer

(D) -273°C

Explanation

Solution: The kinetic energy of the molecules is Zero at absolute zero temperature (0K) as all the molecules will be at rest at this temperature.