A company has an order for 792 kg of a flame-retardant powder. The powder can be made by pathway P or pathway Q.
For each pathway, the reactants are mixed in the mass proportions shown by the balanced equation. The company wants to limit the mass of raw materials it purchases and keep waste-disposal costs low.
| Pathway | Atom economy (%) | Percentage yield (%) | What happens to the by-products |
|---|---|---|---|
| P | 88.0 | 90.0 | They are harmful and must be treated before disposal. |
| Q | 75.0 | 96.0 | They are all sold for use as raw materials in another process. |
Calculate the total mass of reactants required to make 792 kg of flame-retardant powder using each pathway.
Show your working.
Evaluate which pathway the company should use.
152 exam-style questions on OCR GCSE Chemistry 5.1 Monitoring chemical reactions, covering 5.1.1 The technique of titration, 5.1.2 Theoretical mass, percentage yield and atom economy, 5.1.3 Concentration of a solution in mol/dm3, 5.1.4 Concentration calculations and titration results, 5.1.5 Molar gas volume and volumes of gases in reactions, and 5.1.6 Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.