Chemical Engineering Thermodynamics - Study Mode

[#326] Entropy change for an irreversible process taking system and surrounding together is
Correct Answer

(B) > 0

Explanation

Solution: For an isolated system the entropy change is always goes on increasing (second law of thermodynamics). Given, the system and surroundings are taken together that means the resulting system will be an isolated system and in that isolated system if the interactions between the system and surroundings are irreversible we the entropy change will be greater than zero and if the interactions are reversible the entropy change will be equal to zero. $$Delta {S_{isolated,,system}} geqslant 0$$

[#327] The expression for the work done for a reversible polytropic process can be used to obtain the expression for work done for all processes, except reversible __________ process.
Correct Answer

(B) Isothermal

Explanation

Solution: For a polytrophic process we know $$P{V^n} = { ext{constant}}$$ So, the work done in an polytrophic process is $$W = frac{{{P_2}{V_2} - {P_1}{V_1}}}{{n - 1}}$$ So, we can see clearly when $$n = 1$$ xa0the work done is becoming infinity which is wrong conceptually hence the above formulae can’t be applied in case of isothermal $$left( {n - 1}
ight)$$ xa0process.

[#328] In the equation, PV n = constant, if the value of n = 1, then it represents a reversible __________ process.
Correct Answer

(A) Isothermal

Explanation

Solution: For a isothermal process since temperature should remains constant and for an ideal gas undergoing reversible isothermal process can $$b$$ represented by $$PV=nRT.$$

[#329] The internal energy of an ideal gas does not change in a reversible __________ process.
Correct Answer

(A) Isothermal

Explanation

Solution: We know for an ideal gas the internal energy is given by: Actually the internal energy (U) of any substance is a function of $$eqalign{
& dU = CvdT - left[ {P + Tleft( {frac{{left( {frac{{partial V}}{{partial T}}}
ight)p}}{{left( {frac{{partial V}}{{partial P}}}
ight)T}}}
ight)dV}
ight] cr
& { ext{For an ideal gas, }}PV = RT cr
& { ext{So, }}left( {frac{{partial V}}{{partial T}}}
ight)p = frac{R}{P},,{ ext{and }}left( {frac{{partial V}}{{partial P}}}
ight)T = - frac{{RT}}{{{P^2}}} cr
& { ext{Hence, }}dU = CvdT cr} $$ So, in case of isothermal process the internal energy remains constant.

[#330] In the equation PV n = constant, if the value of $${ ext{n}} = gamma = frac{{{{ ext{C}}_{ ext{P}}}}}{{{{ ext{C}}_{ ext{V}}}}},$$ xa0 then it represents a reversible __________ process.
Correct Answer

(C) Isentropic

Explanation

Solution: If the polytrophic index is equal to ratio of heat capacities $$left( gamma
ight)$$ xa0than the process is known as reversible adiabatic process which is also called as isentropic process.