The direct conversion of A to B is difficult, hence it is carried out by the following shown path: Given $\quad \Delta \mathrm{S}_{(\mathrm{A} \rightarrow \mathrm{C})}=50$ e.u. $\Delta \mathrm{S}_{(\mathrm{C} \rightarrow \mathrm{D})}=30$ e.u. $\Delta \mathrm{S}_{(\mathrm{B} \rightarrow \mathrm{D})}=20$ e.u. where e.u. is entropy unit then $\Delta \mathrm{S}_{(\mathrm{A} \rightarrow \mathrm{B})}$ is

JEE Advanced · 2006 · 09 Apr 2006 · Chemical Thermodynamics

The direct conversion of A to B is difficult, hence it is carried out by the following shown path:

Given

Δ S_{(A \to C)} = 50

e.u.

Δ S_{(C \to D)} = 30

e.u.

Δ S_{(B \to D)} = 20

e.u.
where e.u. is entropy unit then

Δ S_{(A \to B)}

(A)+100 e.u.
(B)+60 e.u.✓ Correct
(C)-100 e.u.
(D)-60 e.u.

Answer: (B)

Solution

Entropy is a state function, so the entropy change is path-independent. Using the given path:

Δ S_{(A \to B)} = Δ S_{(A \to C)} + Δ S_{(C \to D)} - Δ S_{(B \to D)}

. Substituting:

Δ S_{(A \to B)} = 50 + 30 - 20 = 60

e.u.

JEE Advanced · 2006 · 09 Apr 2006 · Single correct option

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