# How does partial pressure affect delta G?

Sep 26, 2015

$\Delta G = \Delta {G}^{\circ} + R T \ln \left(\frac{{\left({P}_{N {H}_{3}}\right)}^{2}}{{P}_{{N}_{2}} \cdot {\left({P}_{{H}_{2}}\right)}^{3}}\right)$

#### Explanation:

The relationship between $\Delta G$ and pressure is: $\Delta G = \Delta {G}^{\circ} + R T \ln Q$

Where $Q$ is the reaction quotient, that in case of a reaction involving gaseous reactants and products, pressure could be used.

For example: ${N}_{2} \left(g\right) + 3 {H}_{2} \left(g\right) \to 2 N {H}_{3} \left(g\right)$

The reaction quotient is: $Q = \frac{{\left({P}_{N {H}_{3}}\right)}^{2}}{{P}_{{N}_{2}} \cdot {\left({P}_{{H}_{2}}\right)}^{3}}$

Therefore, $\Delta G = \Delta {G}^{\circ} + R T \ln \left(\frac{{\left({P}_{N {H}_{3}}\right)}^{2}}{{P}_{{N}_{2}} \cdot {\left({P}_{{H}_{2}}\right)}^{3}}\right)$

I recommend this video that explains this concept in details: