The equilibrium constant $\left({\mathrm{K}}_{\mathrm{p}}\right)$ for the formation of ammonia from its constituent elements at $27°\mathrm{C}$ is $1.2\times {10}^{-4}$ and at $127°\mathrm{C}$ is $0.60\times {10}^{-4}.$ Calculate the mean heat of formation of ammonia per mole in this temperature range.