# Methanol can be manufactured from carbon monoxide and hydrogen according to the following reversible reaction:

CO(g) + 2H₂(g) ⇌ CH₃OH(g)     ΔH = −90 kJ mol⁻¹

At a certain temperature, the equilibrium constant, Kc, for this reaction has a value of 2.5 × 10⁴ mol⁻² dm⁶. When the temperature is increased to 400 °C, the value of Kc decreases significantly. Explain what the value of Kc tells us about the position of equilibrium, and explain why increasing the temperature causes Kc to decrease for this reaction.

> Eduqas A-Level Chemistry — 3.8 Equilibrium constants · Explain · 5 marks

## Mark scheme (5 marks)

1. A large value of Kc (2.5 × 10⁴) means the equilibrium lies to the right / towards the products
2. This means the concentration of products (methanol) is much greater than the concentration of reactants at equilibrium
3. The forward reaction is exothermic (ΔH is negative / releases heat)
4. Increasing temperature favours the endothermic (reverse) reaction / equilibrium shifts to the left
5. This means less product and more reactants are present at the new equilibrium, so Kc decreases

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/methanol-can-be-manufactured-from-carbon-5e58725a) · Published by Druglandscape Ltd.