Chemical Engineering Thermodynamics - Study Mode

[#121] In an irreversible process
Correct Answer

(C) Tds - dE + dW< 0

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 $$TdS - dU - delta W = 0$$

[#122] In any spontaneous process,
Correct Answer

(C) Both F and A decreases

Explanation

Solution: For any spontaneous process there should be finite changes so, we can consider it as an irreversible process and we know for irreversible process from second law of thermodynamics $$TdS - dU - PdV > 0$$ Under constant temperature and volume process $$ - dF > 0 Rightarrow dF < 0$$ Similarly for an constant temperature and pressure process $$eqalign{
& dleft( {TS - U - PV}
ight) > 0 cr
& Rightarrow dG = 0 cr} $$

[#123] The enthalpy change when ammonia gas is dissolved in water is called the heat of
Correct Answer

(A) Solution

Explanation

Solution: The enthalpy changes of solution is called the amount of heat evolved or taken by th system to form the solution.

[#124] During adiabatic expansion of gas
Correct Answer

(D) None of these

Explanation

Solution: During adiabatic process the interactions of system with surroundings becomes zero. So, the internal energy of the system is used for doing the expansion work.

[#125] The equation DU = Tds - PdV is applicable to infinitesimal changes occuring in
Correct Answer

(D) A closed system with changes in composition

Explanation

Solution: The given equation is a fundamental property relation and is valid for every open system with constant composition and for a closed system when no reaction is taking place in the system.