中文（繁體）
中文（简体）
English
S5 Chemistry: Metal Extraction (Paper 1: Basics)
S5 Chemistry: Metal Extraction (Paper 1: Basics)
Ten items on the groundwork of metal extraction: the reactivity series and choice of method, blast furnace reactions, limestone, cryolite and aluminium electrolysis, with mole and mass calculations and answers.
Direct answers Answers in order: metals below carbon, carbon monoxide, electrolysis of molten aluminium oxide, water is reduced first, Fe2O3 + 3CO -> 2Fe + 3CO2, slagging out silica, 70.0 percent, 112 g, it lowers the melting point, the more reactive metals need electrolysis.
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: Metal Extraction |
| Level | S5 |
02 Questions (10 items)
- FoundationWhich metals can be extracted from their ores by reduction with carbon?
- FoundationWhen iron is extracted from haematite, which substance actually reduces the iron oxide?
- FoundationBy what method is aluminium obtained from aluminium oxide?
- IntermediateWhy can sodium not be obtained by electrolysing sodium chloride solution?
- IntermediateWrite the equation for the reduction of iron(III) oxide by carbon monoxide in the blast furnace.
- IntermediateWhat is the purpose of adding limestone to the blast furnace?
- ChallengeWhat is the percentage by mass of iron in iron(III) oxide, Fe = 56?
- ChallengeWhat mass of iron can be obtained in theory from 160 g of iron(III) oxide?
- ChallengeWhat is the role of cryolite in the electrolysis of aluminium?
- Error redoA student claims every metal can be extracted by reduction with carbon. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Metals below carbon in the reactivity series, such as zinc, iron, lead and copper. | The more reactive a metal, the more stable its compound, so carbon cannot reduce it; only the less reactive metals yield to carbon. |
| 2 | Carbon monoxide. | Coke burns to carbon dioxide, which reacts with hot carbon to give carbon monoxide, and that gas reduces the iron oxide. |
| 3 | By electrolysis of molten aluminium oxide dissolved in cryolite. | Aluminium is more reactive than carbon, so carbon cannot reduce the oxide; electrolysis must supply the energy instead. |
| 4 | Water is reduced more readily than sodium ions, so only hydrogen is released at the cathode. | In aqueous solution water is discharged first; sodium requires electrolysis of molten sodium chloride with moisture excluded. |
| 5 | Fe2O3 + 3CO -> 2Fe + 3CO2 | One mole of the oxide needs three moles of carbon monoxide, which is oxidised to carbon dioxide. |
| 6 | It decomposes to calcium oxide, which reacts with silica impurities to form calcium silicate slag and removes them. | Limestone is neither fuel nor reducing agent; it forms slag that carries away the refractory sandy impurity. |
| 7 | 70.0 percent | The molar mass is 160 g mol-1 of which iron contributes 112 g mol-1, and 112 over 160 is 0.700. |
| 8 | 112 g | The oxide to iron ratio is one to two, so 1 mol of oxide gives 2 mol of iron, which is 112 g. |
| 9 | It lowers the melting point of aluminium oxide so the cell runs near 1000 degrees and uses less energy. | Pure aluminium oxide melts near 2045 degrees; cryolite dissolves it and greatly lowers the working temperature. |
| 10 | Wrong. Metals such as potassium, sodium, calcium, magnesium and aluminium are more reactive than carbon, so their oxides need electrolysis. | The reactivity series decides the method; carbon reduces only metals below it, the commonest confusion in this topic. |
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 reactivity series from potassium to gold once and draw a line at carbon: electrolysis above, carbon reduction below.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.