O-LevelChemistryChemistry of the Environment5070/22 · May/June 2019 · Q66 Marks

Drinking water is obtained by purification of sea water and river water.

(a)Desalination is used to convert sea water into drinking water. What is desalination?[1]
(b)(i)River water is often polluted by phosphates and nitrates. (i) Give the source of these two pollutants.[1]
(b)(ii)Name one environmental effect caused by these pollutants in river water.[1]
(c)(i)River water can be converted into drinking water. (i) Describe how insoluble solids are removed from river water.[1]
(c)(ii)Name the substance used to remove bad tastes and odours from river water.[1]
(c)(iii)Name the substance used to disinfect river water so it is safe to drink.[1]

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

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Topic: Chemistry of the Environment, O-Level Chemistry (syllabus 5070). Structured question, 6 marks.
Source: O-Level Chemistry, May/June 2019 Paper 2 Variant 2, question 6.

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