$\Delta G_{rxn}^o = 103 - 100.7 = 2.3\,kcal/mol$
$ = 2300\,cal/mol$
$\Delta G_{rxn}^o = - RT\,\ln \,K$
$2300\,cal/mol = - 2\,cal\,mol\,K \times 500\,K \times \ln \,K$
$\ln \,K = 2.3$
$K = 10 \,atm = $Vapour pressure of liquid $'S'$ Vapour pressure of liquid $'S'$ at $500\,K$ is approximately equal to $10\,atm.$
${C_p}$ of ${H_2}{O_{\left( g \right)}}$ $ = 33.58\,J\,{K^{ - 1}}\,mo{l^{ - 1}}$
${C_p}$ of ${H_{2\left( g \right)}}$ $ = 28.84\,J\,{K^{ - 1}}\,mo{l^{ - 1}}$
${C_p}$ of ${O_{2\left( g \right)}}$ $ = 29.37\,J\,{K^{ - 1}}\,mo{l^{ - 1}}$
$\left( i \right)\,2F{e_2}{O_3}\left( s \right) \to 4Fe\left( s \right) + 3{O_2}\left( g \right)$
${\Delta _r}{G^o} = + 1487.0\,kJ\,mo{l^{ - 1}}$
$\left( {ii} \right)\,2CO\left( g \right) + {O_2}(g) \to 2C{O_2}\left( g \right)$
${\Delta _r}{G^o} = - 514.4\,kJ\,mo{l^{ - 1}}$
તો નીચેની પ્રક્રિયા માટે મુક્ત ઊર્જા ફેરફાર $\Delta_rG^o$ .....$kJ\, mol^{-1}$
$\,2F{e_2}{O_3}\left( s \right) + 6CO\left( g \right) \to 4Fe\left( s \right) + 6C{O_2}\left( g \right)$