Given, \(\Delta U=2.1\, \mathrm{kcal}, \Delta n_{g}=2\)

\(R=2 \times 10^{-3}\, \mathrm{kcal}, T=300 \,\mathrm{K}\)

\(\therefore \Delta H=2.1+2 \times 2 \times 10^{-3} \times 300=3.3 \,\mathrm{kcal}\)

Again, \(\Delta G=\Delta H-T \Delta S\)

Given, \(\Delta S=20 \times 10^{-3} \,\mathrm{kcal} \,\mathrm{K}^{-1}\)

On putting the values of \(\Delta \mathrm{H}\) and \(\Delta \mathrm{S}\) in the equation.

we get

\(\Delta G=3.3-300 \times 20 \times 10^{-3}\)

\(=3.3-6 \times 10^{3} \times 10^{-3}\)

\(=-2.7\; \mathrm{kcal}\)