During an industrial water-treatment process, acidic wastewater containing hydrochloric acid, HCl\text{HCl}HCl, is treated by adding sodium hydroxide solution, NaOH\text{NaOH}NaOH.
Explain the type of reaction taking place during this treatment, describing the behavior of the key ions involved.
276 exam-style questions 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 has a worked solution and a mark scheme showing where the marks go.