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| Frage | Antworten |
| What does world food production depend on? | World food production depends nitrogen fertilisers. |
| What are these fertilisers made from? | These fertilisers are made from ammonia. |
| By which process are these made? | These are fertilisers are made from ammonia, which is made by the Haber process. |
| What is the word equation for the Haber process equation? | The word equation for the Haber process equation is: nitrogen + hydrogen ↔ ammonia |
| What is the balanced symbol equation for the Haber process equation? | The balanced symbol equation for the Haber process equation is: N2 + 3H2 ↔ 2NH3 |
| What are the optimum conditions for the Haber process? | The optimum conditions for the Haber process are to: - use a catalyst made of iron - raise the temperature to about 450°C (fairly low for an industrial process) - use high pressure (about 200 atmospheres/20 MPa) - recycle any unreacted nitrogen and hydrogen. |
| The conditions used in the Haber process are designed to make the process as efficient as possible. - What does the iron catalyst do? | - The iron catalyst increases the reaction rate (rate of successful collisions) but not the percentage yield. |
| What does high pressure do? | - High pressure increases the percentage yield of ammonia. |
| What does a high temperature do? | - A high temperature increases reaction rate - A high temperature breaks down ammonia, reducing percentage yield. |
| What is the optimum temperature? | The optimum temperature is 450°C. |
| Why is this temperature used? | Although the yield is not very high, the rate is fairly quick. This is the best compromise or 'best of a bad balance'. |
| When do the costs increase in chemical manufacturing? | Costs increase when the pressure is raised (increasing the plant costs), and the temperature is raised (increasing energy costs). |
| When do costs decrease in chemical manufacturing? | Costs decrease when catalysts are used, unreacted starting materials are recycled and automation is used (reducing wage bills). |
| There are three economic considerations that determine the conditions used to manufacture a chemical. What are they? | These economic considerations determine the conditions used to manufacture a chemical. - Both the reaction rate and the percentage yield must be high enough to give a sufficient daily yield of product. - A low percentage yield can be accepted if the reaction can be repeated many times with recycled starting materials. - Optimum conditions give the lowest cost, rather than the fastest rate or highest yields. |
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