An island needs 5.0 × 106 dm3\mathrm{dm^{3}}dm3 of potable water every day. The island can use two methods to produce potable water. The table gives information about the two methods.
| Method | Energy used to produce 1000 dm3\mathrm{dm^{3}}dm3 of potable water / MJ | Maximum volume that can be produced each day / dm3\mathrm{dm^{3}}dm3 | Treatment needed |
|---|---|---|---|
| distillation of sea water | 250 | no limit | distillation |
| treatment of ground water | 2 | 3.0 × 106 | filtration and chlorination |
Calculate the energy needed each day if all the island's water is produced by distillation of sea water.
Explain why ground water needs to be filtered before use but water produced by distillation does not.
The island council plans to produce all of its potable water from ground water. Evaluate this plan. Use the information in the table and your own knowledge.
48 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.