The change in Gibbs Free energy is given by ΔH=ΔU+ΔngRT
where ΔH is the enthalpy of the reaction ΔS is the entropy of the reaction and ΔU is the change in internal energy Δng is the (number of gaseous moles in product) - (number of gaseous moles in reactant )=2−0=2 R is the gas constant =2 cal But, ΔH=(2.1×103)+(2×2×300)=3300cal
Hence, ΔG=ΔH=TΔS ΔG=3300−(300×20) ΔG=−2700cal=−2.7cal