# Nitrogen and hydrogen react in a closed container to form ammonia according to the equation: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). The reaction reaches equilibrium. Explain how the value of Kp changes, if at all, when (i) the temperature is increased and (ii) the pressure is increased, given that the forward reaction is exothermic.

> AQA A-Level Chemistry (7405) — 3.1.10 Equilibrium constant Kp (A-Level only) · Explain · 5 marks

> The industrial production of ammonia involves a reversible reaction between nitrogen and hydrogen gases. At equilibrium, all three gases are present in the closed system.

## Mark scheme (5 marks)

1. Kp does not change when pressure is increased
2. Kp only changes when temperature changes (not pressure)
3. Increasing temperature causes Kp to decrease
4. Because the forward reaction is exothermic, increasing temperature favours the reverse (endothermic) reaction
5. The shift towards reactants means the proportion of ammonia decreases, so Kp decreases (linking position of equilibrium to Kp value)

## Key terms

- [Kp](https://www.gradenine.co.uk/glossary/kp)
- [equilibrium](https://www.gradenine.co.uk/glossary/equilibrium)
- [exothermic](https://www.gradenine.co.uk/glossary/exothermic)

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Source: [GradeNine](https://www.gradenine.co.uk/q/nitrogen-and-hydrogen-react-in-a-e6d7c6cd) · Published by Druglandscape Ltd.