A railway company is considering changing the electricity supply used by its electric trains. The table gives the mass of carbon dioxide released for each kWh of electricity supplied by different sources.
| Source of electricity | Mass of carbon dioxide released (g per kWh) |
|---|---|
| Renewable-energy generators | 14 |
| Nuclear power | 20 |
| Gas-fired power station | 510 |
| Gas-fired power station with carbon capture | 190 |
The percentages of electricity from each source would be as follows.
| Source of electricity | Existing supply | New supply |
|---|---|---|
| Renewable-energy generators | 25% | 40% |
| Nuclear power | 25% | 30% |
| Gas-fired power station | 50% | 0% |
| Gas-fired power station with carbon capture | 0% | 30% |
The railway company uses 2.4 × 10⁸ kWh of electricity each year. It wants the change to reduce its annual carbon dioxide emissions by at least 46 500 tonnes.
For this question, 1 tonne = 1 000 000 g.
Calculate the mean mass of carbon dioxide released per kWh for the existing supply and for the new supply.
Calculate the reduction in the mass of carbon dioxide released in one year if the new supply is used. State whether the railway company reaches its target.
109 exam-style questions on OCR GCSE Chemistry 6.3 Interpreting and interacting with earth systems, covering 6.3.1 Formation and evolution of the atmosphere, 6.3.2 The greenhouse effect and climate change, 6.3.3 Sources and problems of atmospheric pollutants, and 6.3.4 Producing potable water. Each one has a worked solution and a mark scheme showing where the marks go.