Acids, alkalis and pH
Acids, alkalis and pH
An acid is a source of hydrogen ions, H+\text{H}^{+}H+, when dissolved in water. An alkali is a soluble base and is a source of hydroxide ions, OH−\text{OH}^{-}OH−, in water.
Step-by-step lessons on Edexcel GCSE Chemistry 4.1 Acids, covering 4.1.1 Acids, alkalis and the pH scale, 4.1.2 Hydrogen ion concentration and pH, 4.1.3 Dilute and concentrated, weak and strong acids, 4.1.4 Bases, alkalis and the reactions of acids, 4.1.5 Chemical tests for hydrogen and carbon dioxide, 4.1.6 Neutralisation as a reaction of acids with bases, 4.1.7 Preparing soluble salts, and 4.1.8 Solubility rules and preparing insoluble salts. Each one builds up to exam-style questions. Nail the core quantitative topics — moles, balancing equations and calculations — early on, since they underpin higher-tier questions across every paper and topic.