# A student has four separate solutions, each containing one of the following ions: Fe²⁺, Fe³⁺, Cu²⁺, or Zn²⁺. The student adds an excess of sodium hydroxide solution to each solution and observes the precipitate formed. Describe the observations the student would make for each of the four solutions when excess sodium hydroxide solution is added.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 2.5 Tests for ions and gases · Describe · 4 marks

> Each solution is colourless except the copper(II) solution, which is pale blue. The student adds excess sodium hydroxide solution to each solution in turn.

## Mark scheme (4 marks)

1. Fe²⁺ gives a green precipitate with sodium hydroxide solution
2. Fe³⁺ gives a red-brown (or orange-brown) precipitate with sodium hydroxide solution
3. Cu²⁺ gives a blue precipitate with sodium hydroxide solution
4. Zn²⁺ gives a white precipitate that dissolves in excess sodium hydroxide solution (forming a colourless solution)

## Key terms

- [precipitate](https://www.gradenine.co.uk/glossary/precipitate)
- [sodium hydroxide solution](https://www.gradenine.co.uk/glossary/sodium-hydroxide-solution)
- [excess](https://www.gradenine.co.uk/glossary/excess)
- [Fe²⁺](https://www.gradenine.co.uk/glossary/fe)
- [Fe³⁺](https://www.gradenine.co.uk/glossary/fe)
- [Cu²⁺](https://www.gradenine.co.uk/glossary/cu)
- [Zn²⁺](https://www.gradenine.co.uk/glossary/zn)

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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