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S5 Chemistry: Industrial Processes (Paper 1: Basics)
S5 Chemistry: Industrial Processes (Paper 1: Basics)
Ten items on the groundwork of industrial processes: raw materials, catalysts, mole ratios and yield arithmetic for the Haber and Contact processes, with answers and notes.
Direct answers Answers in order: nitrogen and hydrogen, iron, vanadium(V) oxide, exothermic so low temperature helps but the rate is slow, 2 mol, 8 mol, 2 mol, an acid mist forms so concentrated acid is used, 7.2 mol, a catalyst does not change the equilibrium yield.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S5 Chemistry: Industrial Processes |
| Level | S5 |
02 Questions (10 items)
- FoundationWhich two gases are the raw materials for making ammonia in the Haber process?
- FoundationWhich catalyst is used in the Haber process?
- FoundationWhich catalyst is used in the Contact process for making sulphuric acid?
- IntermediateThe Haber process has dH = -92 kJ mol-1. What does that imply for the choice of temperature?
- IntermediateIn the Haber process, what is the minimum amount of nitrogen needed to react completely with 6 mol of hydrogen?
- IntermediateIf 4 mol of nitrogen react completely, what is the theoretical amount of ammonia formed?
- ChallengeIn the Contact process, 2 mol of sulphur is burned and then oxidised. What is the theoretical amount of sulphur trioxide formed?
- ChallengeWhy is sulphur trioxide not passed straight into water in the Contact process?
- ChallengeIf 90 per cent of 8 mol of sulphur dioxide is converted, how much sulphur trioxide is obtained?
- Error redoA student says that adding a catalyst raises the yield of ammonia. Is that correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Nitrogen and hydrogen | Nitrogen comes from fractional distillation of air and hydrogen is usually made by steam reforming of natural gas; the two combine over a catalyst to give ammonia. |
| 2 | Iron, with small amounts of potassium oxide and aluminium oxide as promoters | The iron catalyst lowers the activation energy so an acceptable rate is reached at a workable temperature. |
| 3 | Vanadium(V) oxide, V2O5 | The vanadium catalyst makes sulphur dioxide oxidise fast enough at 400 to 450 degrees C without needing a still higher temperature. |
| 4 | It is exothermic, so a low temperature favours ammonia, but the rate is then too slow, so about 450 degrees C is used as a compromise | A negative dH means the forward reaction releases heat, so raising the temperature shifts the equilibrium back and lowers the yield. |
| 5 | 2 mol | The equation N2 + 3H2 -> 2NH3 gives a hydrogen to nitrogen ratio of 3 to 1, so 6 mol of hydrogen needs 2 mol of nitrogen. |
| 6 | 8 mol | Each mole of nitrogen gives two moles of ammonia, so 4 mol of nitrogen gives at most 8 mol of ammonia. |
| 7 | 2 mol | Sulphur atoms are conserved through the plant, so each mole of sulphur gives one mole of sulphur dioxide and then one mole of sulphur trioxide. |
| 8 | It forms a dense acid mist that is hard to absorb and hazardous; concentrated sulphuric acid is used as the absorbing liquid instead | The reaction with water is so violent that a mist of acid droplets forms and is difficult to collect. |
| 9 | 7.2 mol | 8 times 0.9 is 7.2; the 0.8 mol of sulphur dioxide left over is recycled back to the converter. |
| 10 | No. A catalyst only speeds up the approach to equilibrium, so the equilibrium yield is unchanged | A catalyst speeds up the forward and reverse reactions equally, so neither the equilibrium constant nor the yield changes. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Write the Haber and Contact process equations once each and circle the catalyst in both.Tutor Registration →
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