# For the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g), explain how an increase in total pressure at constant temperature affects the position of equilibrium and the value of Kc.

> IB DP Chemistry Higher Level (2023 syllabus) — R2.3 How far? The extent of chemical change · Explain · 4 marks

## Mark scheme (4 marks)

1. An increase in pressure shifts the position of equilibrium to the right / towards the side with fewer moles of gas.
2. Because increasing pressure increases the concentration (or partial pressure) of all gaseous species, the system responds to reduce the pressure / number of moles of gas, in accordance with Le Chatelier's principle.
3. The value of Kc remains unchanged / constant.
4. Kc depends only on temperature; since temperature is constant, Kc is unchanged even though the concentrations of individual species change.

## Key terms

- [position of equilibrium](https://www.gradenine.co.uk/glossary/position-of-equilibrium)
- [Kc](https://www.gradenine.co.uk/glossary/kc)
- [total pressure](https://www.gradenine.co.uk/glossary/total-pressure)

## Related

- [Revision notes for IB DP Chemistry Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/for-the-equilibrium-n-g-3h-g-79afa5d4) · Published by Druglandscape Ltd.