Consider this reaction:

N2 (g) + 3H2 (g) 2NH3 (g)

What will happen if more hydrogen gas is added to the reaction mixture?

There will be a shift toward the products.

There will be a shift toward the reactants.

There will not be a shift in equilibrium.

The value for Keq will change.

The answer is There will be a shift toward the reactants.

To solve this problem, it is necessary to understand Le Chatelier's principle. According to the principle, if a chemical reaction undergoes changes in conditions, the chemical equilibrium will shift in order to undo the effects. In the reaction N2 (g) + 3H2 (g) ⇄ 2NH3 (g), when hydrogen gas is added to the reaction mixture, the concentration of chemicals will increase in the mixture. The system will try to decrease the concentration by removing H2, so the equilibrium will be shifted toward the reactants.