# Explain why silicon dioxide does not dissolve in water, whilst sulfur dioxide dissolves readily and forms an acidic 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. Silicon dioxide has a giant covalent (macromolecular) structure
2. Many strong covalent bonds must be broken in silicon dioxide, requiring too much energy for water to overcome
3. Sulfur dioxide has a simple molecular structure / consists of discrete molecules
4. Sulfur dioxide reacts with water to form sulfurous acid (H₂SO₃)
5. Sulfurous acid dissociates / ionises in water to release H⁺ ions, making the solution acidic

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