Chemical Engineering Thermodynamics - Study Mode

[#271] Enthalpy changes over a constant pressure path are always zero for __________ gas.
Correct Answer

(B) A perfect

Explanation

Solution: Since a perfect gas can also be considered as an ideal gas and for ideal gas hence at constant pressure the temperature remains constant and for ideal gas since enthalpy is solely a function of temperature we can say enthalpy is zero.

[#272] Thermal efficiency of a Carnot engine can approach 100%, only when the temperature of the
Correct Answer

(C) Either A or B

Explanation

Solution: Since Efficiency of a Carnot engine is $$aleph = 1 - frac{{{T_2}}}{{{T_1}}}$$ So, when the cold reservoir temperature is zero or when the hot reservoir temperature is infinity we can say that the efficiency is $$100\% .$$ But this is purely an impossible situation even under ideal conditions as given by second law of thermodynamics.

[#273] 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
Correct Answer

(B) 2

Explanation

Solution: $$f = C - phi + 2 + { ext{ number of chemical reactions}} + { ext{ number of constraints}}$$ $$ Rightarrow { ext{ given number of components}} = 3$$ Number of phase $$=2,$$ xa0number of independent chemical reactions $$=1,$$ xa0number of constraints $$= 1$$ xa0(initially only $$A$$ is present) So, $$f=2$$

[#274] Mollier diagram is a plot of
Correct Answer

(C) Entropy vs. enthalpy

Explanation

Solution: Mollier diagram is a plot between the enthalpy and entropy and it is very useful during phase change calculations.

[#275] For a multicomponent system, the term chemical potential is equivalent to the
Correct Answer

(C) Partial molar free energy

Explanation

Solution: For multicomponent system the chemical potential is defined as partial Gibbs free energy. $${mu _i} = left( {frac{{partial nG}}{{partial {n_i}}}}
ight)T,P,{n_j}$$