The gas phase reaction 2A(g) ⇌ A _ 2 (g) at 400K has Δ G ^ o = + 25...

Using formula

${\Delta}_{r}{G}^{0} = - {RTlnK}_{p}$

$25200 = - 2 . 3 \times 8 . 3 \times 400\log \left({K}_{p}\right)$

${K}_{p} = {10}^{- 3 . 3} = {10}^{- 3} \times 0 . 501$

$= 5 . 01 \times {10}^{- 4}{Bar}^{- 1}$

$= 5 . 01 \times {10}^{- 9}{Pa}^{- 1}$

$= \dfrac{{K}_{C}}{8 . 3 \times 400}$

${K}_{C} = 1 . 66 \times {10}^{- 5}{m}^{3} / mole$

$= 1 . 66 \times {10}^{- 2}L / mol$

$= 2$

Gibbs free energy can be visualized as the amount of useful energy present in a thermodynamic system that can be utilized to perform some useful work.