JEE Advanced 2021 Paper 1 · Q08 · Chemical Equilibrium & Le Chatelier

Question

The value of $\Delta S^\circ$ (in J K$^{-1}$ mol$^{-1}$) for the given reaction, at 1000 K is ___.

SolveKar AI · Accepted Answer

From the regression ln(p$_Z$/p$^\circ$) = -$\Delta H^\circ$/(RT) + $\Delta S^\circ$/R, substitute one known point on the line — take (10$^4$/T = 10, ln = -3), i.e. T = 1000 K and ln(p$_Z$/p$^\circ$) = -3. We already have $\Delta H^\circ$ = 2R \* 10$^4$ from Q.7.

Substituting: -3 = -[2R \* 10$^4$/(R \* 1000)] + $\Delta S^\circ$/R = -20 + $\Delta S^\circ$/R.

So $\Delta S^\circ$/R = -3 + 20 = 17 → $\Delta S^\circ$ = 17 \* 8.314 J K$^{-1}$ mol$^{-1}$ = 141.338 ≈ 141.34 J K$^{-1}$ mol$^{-1}$.

JEE Advanced 2021 Paper 1 · Q08 · Chemical Equilibrium & Le Chatelier

Solution