Question

For the reaction 4NH3(g) + 3O2(g)= 2N2(g)+ 6H2O(l), ∆H<0. How will the amount of ammonia at equilibrium be affected by
1 Removing O2
2 Adding N2
3 Adding H2O
4 Decreasing the pressure
5 increasing the temperature

Answer 1

1 Removing O₂

Increased! If oxygen is removed, the equilibrium shifts toward the reactants, producing more ammonia.

2 Adding N₂

Increased! If more nitrogen gas is added it shifts the equilibrium towards the reactants again, causing more ammonia to build up.

3 Adding H₂O

Increased! Same effect as for adding N₂, addition of more products causes the shift towards the reactants.

4 Decreasing the pressure

Decreased! We have 7 mol of reactants vs 8 mol of products, so the products cause higher pressure in the system. If we decrease the pressure, system counteracts to the change producing more products, and reducing amount of ammonia.

5 Increasing the temperature

Increased! Heat is produced in this reaction (exothermic reaction). So additional temperature rise shifts the equilibrium towards the reactants, thus more ammonia is produced.