A catering service is preparing food trays for a run of meals. Under the single-use option, a new tray is needed for every meal. Under the reusable option, the same tray remains in service throughout the run and is washed after each meal. At the end of the run, all trays involved are disposed of.
| Tray | Mass of one tray in g | Energy used in manufacture in MJ/kg | Energy used in disposal per tray in MJ | Energy used during each use, including washing, in MJ |
|---|---|---|---|---|
| Single-use | 18 | 70 | 0.08 | 0 |
| Reusable | 240 | 50 | 0.50 | 0.20 |
Calculate the minimum number of meals in the run for which choosing the reusable tray uses less energy in total than choosing single-use trays.
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99 exam-style questions on AQA GCSE Chemistry 10.2 Life cycle assessment and recycling, covering 10.2.1 Life cycle assessment and 10.2.2 Ways of reducing the use of resources. Each one has a worked solution and a mark scheme showing where the marks go.