$ \Delta \mathrm{U}=\mathrm{Q}+\mathrm{W}, $
$ \Delta \mathrm{U}=0: \text { Process is isothermal } $
$ \mathrm{Q}=-\mathrm{W} $
$ \mathrm{W}=-\mathrm{P}_{\text {ext }} \Delta \mathrm{V}: \text { Irreversible } $
$ =-80 \times 10^3(45-30) \times 10^{-3} $
$ =-1200 \mathrm{~J}$
$A + B \rightleftharpoons C+D$
$27^{\circ}\,C$ પર પ્રમાણિત મુક્ત ઊર્જા ફેરફાર $\left(\Delta_{ r } G ^0\right)$ $(-)$ $............kJ mol ^{-1}$ છે. (નજીકની પૂર્ણાંક)
(આપેલ : $R =8.3\,Jk ^{-1}\, mol ^{-1}$ અને In $10=2.3$ )
$ PbO$$(yellow)$ $\rightarrow$ $PbO$$(red)$