The entropy values (in JK^ -1 ~mol^ -1 ) of H_2(~g)=130.6, Cl_2(~g)=223.0 and HCl(g)=186.7 at 298 K and 1 atm pressure. Then entropy change for the reaction : H_2(~g)+Cl_2(~g) 2 HCl(g) is :

Correct answer: D. +19.8 aligned Δ S^ & =2 S^ _ HCl -(S_ H_2 ^ +S^ _ Cl_2 ) & =2 × 186.7-(130.6+223.0) & =19.8 JK^ -1 ~mol^ -1 aligned

JIPMER 2006

JIPMER 2006 · Chemistry · Thermodynamics (C)

The entropy values (in JK^ -1 ~mol^ -1 ) of H_2(~g)=130.6,...

The entropy values (in

\mathrm{JK}^{-1} \mathrm{~mol}^{-1}

)

of \mathrm{H}_2(\mathrm{~g})=130.6, \quad \mathrm{Cl}_2(\mathrm{~g})=223.0 \quad

and

\mathrm{HCl}(\mathrm{g})=186.7

at 298 K and 1 atm pressure. Then entropy change for the reaction :

\mathrm{H}_2(\mathrm{~g})+\mathrm{Cl}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{HCl}(\mathrm{g})

is :

D. +19.8

\begin{aligned} \Delta S^{\circ} & =2 S^{\circ}{ }_{\mathrm{HCl}}-\left(S_{\mathrm{H}_2}^{\circ}+S^{\circ}{ }_{\mathrm{Cl}_2}\right) \\ & =2 \times 186.7-(130.6+223.0) \\ & =19.8 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\end{aligned}