Question

Ammonia dissociates to give nitrogen and hydrogen. What happens if the pressure is increased on the system at equilibrium?

Short answer

Answer: The system will react to the increase in pressure by shifting the equilibrium position towards the reactants (NH\(_3\)), which have fewer gas moles. This results in an increase in the concentration of NH\(_3\) and decreases in the concentrations of N\(_2\) and H\(_2\). The equilibrium constant remains unchanged.

Step-by-step solution

Write down the balanced chemical equation of the reaction at equilibrium

The balanced chemical equation for the dissociation of ammonia into nitrogen and hydrogen is: NH\(_3\)(g) \(\rightleftharpoons\) 1/2 N\(_2\)(g) + 3/2 H\(_2\)(g)

Identify the moles of gas on each side of the equation

Identify the number of moles of reactants and products on each side of the equation. For the reactants, we have: 1 mol of NH\(_3\)(g) For the products, we have: 1/2 mol of N\(_2\)(g) + 3/2 mol of H\(_2\)(g) = 2 mol of gas products

Apply Le Chatelier's Principle

According to Le Chatelier's Principle, when the pressure on a system in equilibrium is increased, the system shifts in a direction that reduces the pressure. In this case, we must determine whether the reaction shifts towards the reactants or the products to reduce pressure. Since we have fewer moles of gas on the reactants side (1 mol) than on the products side (2 mol), the system will shift towards the reactants, as this will result in fewer gas particles and lower pressure.

Determine the effect of the shift on the system

When the system at equilibrium shifts towards the reactants due to the increase in pressure, the dissociation of ammonia will be suppressed. This means that the concentration of NH\(_3\) will increase and the concentrations of N\(_2\) and H\(_2\) will decrease. As a result, the equilibrium constant of the reaction will remain unchanged, but the position of equilibrium will shift to favor the formation of reactants.

Conclusion

The system will react to the increase in pressure by shifting the equilibrium position towards the reactants (NH\(_3\)), where there are fewer gas moles. This will cause an increase in the concentration of NH\(_3\) and decreases in the concentrations of N\(_2\) and H\(_2\). The equilibrium constant remains unchanged.