Chemical Engineering Thermodynamics MCQ Questions & Answers | Chemical Engineering

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

For thermodynamic equilibrium to satisfy by a system the system should satisfies three conditions
I. Temperature should be same between the phases.
II. Pressure should be same between the phases.(actually the system should not include in any of the work with the surroundings not only in expansion work).
III. Chemical potential between the phases should be same which ensures the equilibrium in mass transfer between the phases.

An extensive property is the one which depend on extent (mass) all the energies like Gibbs free energy, Helmholtz energy, internal energy are extensive properties.

The chemical potential is nothing but partial molar gibbs free energy (since the partial molar functions tells about the change in total molar property with change in composition(moles) we consider partial molar functions as intensive properties),
$${\mu _i} = \left( {\frac{{\partial nG}}{{\partial {n_i}}}} \right)T,P,{n_j}$$
When there is only one component ,G(total molar gibbs free energy) becomes independent of composition(intensive property ) so the equation becomes $${\mu _i} = G\left( {\frac{{\partial {n_I}}}{{\partial {n_i}}}} \right)T,P,{n_j}$$
Hence, $${\mu _i} = G$$

From second law of thermodynamics
$$\eqalign{ & TdS \geqslant \delta Q \cr & \Rightarrow TdS \geqslant dU + \partial W \cr} $$
For an irreversible process $$TdS \geqslant dU + \partial W > 0$$
So, the entropy will be greater than zero for an spontaneous(irreversible ) process only when the internal energy and work done are zero so, for an exothermic reaction since the internal energy is not zero we can say the entropy need not be greater than zero.

We know $$\ln \left( {\frac{f}{{{f^{sat}}}}} \right) = \frac{v}{{RT}}\left( {p - {p^{sat}}} \right)$$      substituting the suitable values we will get $$f=6753.5$$

$${C_P} - {C_V} = R,$$   is valid for ideal gas and we can prove this by using $$T-dS$$  equations.

During the phase transition the pressure and temperatures remain constant and the volume changes since solids, liquids and gases have different volume.

The specific heat is the amount of heat required to change the temperature of the substance from by unit degree. Since during saturated conditions latent heat conversion only takes place and temperature remains constant the situation appears like the system is of infinite strength and there is no change in thermal energy and hence the heat capacity is infinity.