The standard free energy change ( $\Delta \mathrm{G}^{\circ}$ ) for $50 \%$ dissociation of $\mathrm{N}_2 \mathrm{O}_4$ into $\mathrm{NO}_2$ at $27^{\circ} \mathrm{C}$ and 1 atm pressure is $-x \mathrm{~J} \mathrm{~mol}^{-1}$. The value of $x$ is $\_\_\_\_$ (Nearest Integer)
[Given: $\mathrm{R}=8.31 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}, \log 1.33=0.1239 \ln 10=2.3$ ]