For the reaction X(s)⇌Y(s)+Z(g), the plot of lnp⊖pz versus T104 is given below (in solid line), where pz is the pressure (in bar) of the gas Z at temperature T and Pθ=1 bar.
(Given, d(T1)d(lnK)=−RΔH⊖, where the equilibrium constant, K=p⊖pz and the gas constant, R=8.314JK−1mol−1)
The value of ΔS⊖ (in JK−1mol−1) for the given reaction, at 1000 K is ____.
Answer: 141.33
Solution
From the previous question, ΔH⊖=166.28 kJ/mol = 166280 J/mol
From the graph, when T104=10, we have T=1000 K and ln(pz/p⊖)=−3
Using: lnK=−RTΔH⊖+RΔS⊖
−3=−8.314×1000166280+8.314ΔS⊖
−3=−20+8.314ΔS⊖
8.314ΔS⊖=17
ΔS⊖=17×8.314=141.34 J K⁻¹ mol⁻¹
JEE Advanced · 2021 · 03 Oct 2021 · Paper 1 · Numerical answer