WJEC GCSE Chemistry: Acids, salts and analysis (Unit 2.2) overview

The Acids, salts and analysis module covers WJEC Unit 2 topic 2.2. It is the practical heart of the course: how acids behave, how to make salts in the lab, and how to identify unknown substances using chemical tests. This page maps the module and links to a focused answer page for each part.

The topics in this module

Acids, bases and the pH scale

Properties of acids and bases, the H+ and OH- ions, the pH scale and indicators. See Acids, bases and the pH scale.

Neutralisation and reactions of acids

Neutralisation in terms of ions, and the products of acids with metals, bases and carbonates. See Neutralisation and reactions of acids.

Preparing salts

Making a pure dry soluble salt with excess insoluble solid and crystallisation, and making an insoluble salt by precipitation. See Preparing salts.

Tests for gases and cations

Tests for hydrogen, oxygen, carbon dioxide and chlorine, flame tests, and cation precipitates with sodium hydroxide. See Tests for gases and cations.

Tests for anions

Halides with silver nitrate, sulfates with barium chloride, and carbonates with dilute acid. See Tests for anions.

How this module fits the exam

These topics sit in Unit 2, assessed on the Unit 2 written paper (1 hour 45 minutes, 80 marks, 45%). Questions test equations, salt preparation methods, and identifying ions and gases from observations.

How to study this module

1. Learn the ions. Acids give H+, alkalis give OH-, and neutralisation makes water.
2. Master the three acid reactions. Metal (salt + hydrogen), base (salt + water), carbonate (salt + water + carbon dioxide).
3. Practise salt prep. Excess solid then crystallise for soluble salts; precipitation for insoluble salts.
4. Build a tests table. Gases, flame colours, hydroxide precipitates, and anion tests.
5. Solve unknowns. Combine clues to identify an ion or gas in WJEC-style questions.

Then test yourself with the module quiz.