| Describe the haber process. | 1)nitrogen (extracted from the air) and hydrogen (obtained from natural gas) are pumped through pipes
2)the pressure of the mixture of gases is increased to 200 atmospheres
3)the pressurised gases are heated to 450°C and passed through a tank containing an iron catalyst
4)the reaction mixture is cooled so that ammonia liquefies and can be removed
5)unreacted nitrogen and hydrogen are recycled |
| What is a fertiliser? | A nutrient added to soil which increases fertility by providing mineral ions needed for healthy growth in plants. |
| What is an NPK fertiliser? | A fertiliser containing nitrogen, phosphorus and potassium, these are all soluble so can dissolve in water absorbed by root hair cells. |
| Give the 3 ions involved in fertilisers and the minerals they produce. | 1)ammonium ions, NH4+, and nitrate ions, NO3-, are sources of soluble nitrogen
2)phosphate ions, PO43-, are a source of soluble phosphorus
3)all common potassium compounds dissolve in water to produce potassium ions, K+ |
| Why can't phosphate rock be used as a source of phosphate in fertilisers? | Its insoluble however when reacted with acids useful soluble ions are formed:
Nitric acid - Calcium nitrate and phosphoric acid
Sulfuric acid - Single superphosphate
Phosphoric acid - Triple superphosphate (calcium phosphate) |
| Why is ammonia important in fertilisers? | 1)It gets oxidised to make nitric acid (HNO3), which is the source of the nitrate ion (NO3-).
2)Ammonia can be neutralised by nitric acid, to make the salt ammonium nitrate (NH4NO3). This can be represented by the following equation:
Ammonium hydroxide + nitric acid → ammonium nitrate + water
NH4OH + HNO3 → NH4NO3 + H2O |
| What are the 3 key conditions in the haber process? | 1)temperature of 450°C
2)pressure of 200 atmospheres
3)an iron catalyst |
| What are the 3 stages of making sulfuric acid? | 1)sulfur + oxygen → sulfur dioxide
2)sulfur dioxide + oxygen ⇌ sulfur trioxide
3)sulfur trioxide + water → sulfuric acid |
| How is ammonium sulfate made in a lab? | 1)25 cm3 of ammonia solution is measured using a measuring cylinder or pipette and poured into a conical flask.
2)Two drops of methyl orange indicator are added. This will turn yellow in the alkaline ammonia solution.
3)Dilute sulfuric acid is added from a burette slowly until the methyl orange indicator turns orange. If too much acid is added it will turn red.
4)The volume of sulfuric acid which has been added is recorded, and then the neutral solution of ammonium sulfate which contains the indicator is thrown away.
5)The experiment is repeated without the indicator but with the same volumes of ammonia and sulfuric acid.
6)The ammonium sulfate is crystallised by evaporating the |
| Why does the pressure need to be high in the haber process? | increasing the pressure of the reaction mixture will cause the equilibrium position to move to the side with the fewest moles of gas, to reduce the pressure. Yield of ammonia therefor increases |
| Why is the temperature high in the haber process? | When the temperature is increased, the position of equilibrium moves in the endothermic direction to reduce the temperature.
In the Haber process, the forwards reaction is exothermic, so the reverse reaction is endothermic. |
| Why is a catylist used in the haber process? | A catalyst speeds up the rate of the forward and reverse reactions equally. This reduces the time taken for the system to reach equilibrium but it does not affect the position of equilibrium or the yield of ammonia. |
| Give another way of reducing costs in the haber process? | Most of the unreacted hydrogen and nitrogen recycled |
