In the purification of brackish groundwater for domestic use, the final treatment phase involves dosing the water with chlorine gas, Cl2\text{Cl}_2Cl2.
State the primary chemical or biological purpose of this chlorination step.
107 exam-style questions on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one has a worked solution and a mark scheme showing where the marks go.