Chemical Engineering Thermodynamics - Study Mode

[#256] Degree of freedom of a system consisting of a gaseous mixture of H 2 and NH 3 will be
Correct Answer

(D) 3

Explanation

Solution: Given, number of components $$= 2$$ Number of phases $$= 1$$ So, degree of freedom [x08egin{array}{l}
f = C - emptyset + 2\
Rightarrow 2 - 1 + 2\
Rightarrow 3\
F = 3
end{array}]

[#257] A closed system is cooled reversibly from 100°C to 50°C. If no work is done on the system
Correct Answer

(B) U and S both decreases

Explanation

Solution: Since here heat is taken from the system [Q = - ve] From second law of thermodynamics [TdS ge delta Q] Since given reversible process [TdS = delta Q] $$ Rightarrow dS = - ve$$ From first law of thermodynamics $$eqalign{
& delta Q = dU cr
& Rightarrow dU = - ve cr} $$

[#258] The expression for entropy change given by, $$Delta S = - nRlnleft( {frac{{{P_2}}}{{{P_1}}}}
ight),$$ xa0 xa0holds good for
Correct Answer

(B) Reversible isothermal volume change

Explanation

Solution: We know $$S$$ as a function of $$T$$ and $$P$$ as : $$dS = frac{{{C_P}dT}}{T} - {left( {frac{{partial V}}{{partial T}}}
ight)_P}dP$$ For isothermal change $$dT = 0$$ xa0 for ideal gas $$frac{{partial V}}{{partial {T_P}}} = frac{{nR}}{P}$$ $${ ext{So, }}dS = - nRlnleft( {frac{{{P_2}}}{{{P_1}}}}
ight)$$ For isothermal volume change of an ideal gas for both reversible and irreversible process.

[#259] For any system, what is the minimum number of degrees of freedom?
Correct Answer

(B) 0

Explanation

Solution: The degree of freedom means the minimum number of intensive variables which are needed to specify the system and its minimum value is zero. Triple point of a substance is one of the state for which the degree of freedom $$= 0.$$

[#260] Which of the following is not a unit of the equilibrium constant K p ? (where, Δx = number of moles of products number of moles of reactants)
Correct Answer

(D) (atm) Δx 2 , when Δx > 0

Explanation

Solution: The equilibrium constant $$left( {{K_P}}
ight)$$ xa0 for the reaction below can be written as : $${K_P} = {left( {atm}
ight)^{Delta x}}$$ Where $$Delta x = $$ xa0 change in number of moles (difference in number of moles of products $$-$$ reactants).