# Explain why aluminium oxide does not dissolve in water, yet reacts with both dilute hydrochloric acid and dilute sodium hydroxide solution.

> AQA A-Level Chemistry (7405) — 3.2.4 Properties of Period 3 elements and their oxides (A-Level only) · Explain · 5 marks

## Mark scheme (5 marks)

1. Aluminium oxide is amphoteric
2. Aluminium oxide has a giant ionic/lattice structure with strong electrostatic forces between ions, so it does not dissolve in water
3. Aluminium oxide reacts with dilute hydrochloric acid, acting as a base
4. Aluminium oxide reacts with dilute sodium hydroxide solution, acting as an acid
5. The amphoteric nature arises because aluminium is in the middle of Period 3, between the metals (which form basic oxides) and non-metals (which form acidic oxides)

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