A plant nursery uses polypropylene trays to grow seedlings. Each tray is used for 120 growing cycles and is washed after every cycle.
The table shows life-cycle energy data for one tray.
| Stage of the life cycle | Energy used (MJ) |
|---|---|
| obtaining raw materials | 3.6 |
| manufacturing the tray | 1.4 |
| washing after each growing cycle | 0.025 |
| disposal | 0.20 |
Use the data to calculate the mean energy demand for one growing cycle over the tray's whole lifetime.
Give your answer in MJ to 2 significant figures.
Mean energy demand for one growing cycle = ............ MJ
136 exam-style questions on OCR GCSE Chemistry 6.1 Improving processes and products, covering 6.1.1 Extracting metals industrially and by electrolysis, 6.1.2 Life cycle assessment and recycling, 6.1.3 Biological methods of metal extraction, 6.1.4 The Haber process and the production of fertilisers, 6.1.5 Alloys and their uses, 6.1.6 Corrosion and its prevention, 6.1.7 Comparing and selecting materials, and 6.1.8 Industrial conditions, rate and position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.