Q153 · CSIR NET Chemistry, December 2019
Paper: CSIR NET December 2019 · Subject: Physical Chemistry · Chapter: Thermodynamics · Topic: Laws State Functions · Marks: 2 · Difficulty: Medium
Consider the entropy changes in a system undergoing transformation, as depicted in the diagram, below 
The correct statement among the following is (1) $\Delta S_1 = \Delta S_2$ and $\Delta S \neq \Delta S_1 + \Delta S_2$ (2) $\Delta S_1 > \Delta S_2$ and $\Delta S \neq \Delta S_1 + \Delta S_2$ (3) $\Delta S_1 = \Delta S_2$ and $\Delta S = \Delta S_1 + \Delta S_2$ (4) $\Delta S_1 > \Delta S_2$ and $\Delta S = \Delta S_1 + \Delta S_2$
\[ 25^{\circ}\mathrm{C}\ \xrightarrow{\ \Delta S_1\ }\ 50^{\circ}\mathrm{C}\ \xrightarrow{\ \Delta S_2\ }\ 75^{\circ}\mathrm{C} \]
The correct statement among the following is (1) $\Delta S_1 = \Delta S_2$ and $\Delta S \neq \Delta S_1 + \Delta S_2$ (2) $\Delta S_1 > \Delta S_2$ and $\Delta S \neq \Delta S_1 + \Delta S_2$ (3) $\Delta S_1 = \Delta S_2$ and $\Delta S = \Delta S_1 + \Delta S_2$ (4) $\Delta S_1 > \Delta S_2$ and $\Delta S = \Delta S_1 + \Delta S_2$(a)1
(b)2
(c)3
(d)4
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
ΔS₁ = C_p ln(323/298) > ΔS₂ = C_p ln(348/323), and since S is a state function ΔS = ΔS₁ + ΔS₂ — statement (4).
Study loop for Thermodynamics