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S5 Chemistry: Electrolysis – Products and Charge (Paper 1: Basics)
S5 Chemistry: Electrolysis – Products and Charge (Paper 1: Basics)
Ten items on electrode products in molten and aqueous systems, plus charge-to-mole calculations.
Direct answers Answers in order: sodium, chlorine, the anode dissolves, oxygen, 3600 C, hydrogen, 0.10 mol, 2.16 g, chlorine at the anode with hydrogen and sodium hydroxide at the cathode, copper.
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: Electrolysis and Industrial Applications |
| Level | S5 |
02 Questions (10 items)
- FoundationWhat forms at the cathode when molten sodium chloride is electrolysed?
- FoundationWhat forms at the anode when molten sodium chloride is electrolysed?
- FoundationA copper anode is used to electrolyse copper sulphate solution. What happens at the anode?
- IntermediatePlatinum electrodes are used in copper sulphate solution. What forms at the anode?
- IntermediateA current of 2.0 A flows for 30 minutes. What charge passes?
- IntermediateWater with a little sulphuric acid is electrolysed. Which gas appears at the cathode?
- ChallengeElectrolysis of molten sodium chloride passes 9650 C. How many moles of sodium form?
- ChallengeSilver plating passes 0.020 mol of electrons. What mass of silver is deposited?
- ChallengeIn the chlor-alkali process with concentrated brine, what is obtained at each electrode?
- Error redoError replay: a student says oxygen appears at the cathode in copper sulphate solution. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Sodium metal | Reduction happens at the cathode, where sodium ions gain electrons. |
| 2 | Chlorine gas | Chloride ions lose electrons at the anode and pair up into chlorine molecules. |
| 3 | The copper anode dissolves and loses mass | Copper is oxidised more readily than water, so copper atoms lose electrons and enter the solution. |
| 4 | Oxygen | Platinum is inert, so water is oxidised at the anode and oxygen is released. |
| 5 | 3600 C | Convert the time to seconds first: 1800 seconds, then multiply by the current. |
| 6 | Hydrogen | Hydrogen ions are reduced at the cathode, forming hydrogen molecules. |
| 7 | 0.10 mol | One mole of electrons is 96500 C, so 9650 C is 0.10 mol of electrons and sodium is one to one. |
| 8 | 2.16 g | Silver ions take one electron each, giving 0.020 mol of silver, which is 2.16 g. |
| 9 | Chlorine at the anode; hydrogen and sodium hydroxide solution at the cathode | Chloride ions are oxidised at the anode while water is reduced at the cathode, leaving hydroxide ions. |
| 10 | Copper | The cathode reduces, and copper ions are discharged more readily than hydrogen ions, so copper deposits. |
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 electrode reaction first, substitute the numbers second, and use the calculator last.Tutor Registration →
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