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S6 Chemistry: Electrochemical Cells and Fuel Cells (Paper 1: basics)
S6 Chemistry: Electrochemical Cells and Fuel Cells (Paper 1: basics)
Ten basics items on the oxidised electrode in a zinc copper cell, the cell potential, the salt bridge, the copper silver cell, cell notation, the product of a fuel cell, standard conditions, the oxidising agent, moles of electrons and the path of the electrons.
Direct answers Answers in order: the zinc electrode, 1.10 V, it completes the circuit and keeps neutrality, 0.46 V, the anode, water, 298 K with 100 kPa and 1 mol per dm3, the copper ion, 0.40 mol, and electrons go only through the external circuit.
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: S6 Chemistry: Electrochemical Cells and Fuel Cells |
| Level | S6 |
02 Questions (10 items)
- FoundationWhich electrode is oxidised in a zinc copper cell?
- FoundationWhat is the E-cell of a zinc copper cell with Zn as minus 0.76 V and Cu as plus 0.34 V?
- FoundationWhat is the job of the salt bridge?
- IntermediateWhat is the E-cell of a copper silver cell with Cu as plus 0.34 V and Ag as plus 0.80 V?
- IntermediateIn the notation Zn solid, zinc ion, double line, copper ion, copper solid, what does the left side stand for?
- IntermediateWhat is the only product of a hydrogen oxygen fuel cell in use?
- ChallengeWhat are the standard conditions for measuring a standard electrode potential?
- ChallengeWhich ion acts as the oxidising agent in a zinc copper cell?
- ChallengeWhen 0.20 mol of zinc dissolves completely in a cell, how many moles of electrons are transferred?
- Error redoA student says electrons swim through the solution from zinc to copper. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The zinc electrode | Zinc is the more reactive metal, so it loses electrons and is oxidised at the anode. |
| 2 | 1.10 V | The cell potential is cathode minus anode, that is 0.34 minus minus 0.76, which gives 1.10 V. |
| 3 | It completes the circuit and keeps both solutions electrically neutral | Ions move out of the bridge in both directions and cancel the charge build up, so the cell keeps working. |
| 4 | 0.46 V | Silver has the higher potential and is the positive electrode, so 0.80 minus 0.34 gives 0.46 V. |
| 5 | The anode, where oxidation happens | By convention the anode is written on the left and the double line stands for the salt bridge. |
| 6 | Water | Hydrogen is oxidised and oxygen reduced, and they combine to give water only, with no carbon dioxide. |
| 7 | 298 K, 100 kPa and ion concentration of 1 mol per dm3 | Temperature, pressure and concentration must all be at their standard values for the potentials to be comparable. |
| 8 | The copper ion | Copper ions gain electrons and are reduced at the positive electrode, so they are the oxidising agent. |
| 9 | 0.40 mol | Each mole of zinc releases two moles of electrons, so 0.20 times two gives 0.40 mol. |
| 10 | Electrons travel only through the external circuit, while ions carry the current in solution | There are no free electrons in the solution, so only the metal wire carries electrons. |
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.
Decide which electrode is oxidised first, then subtract the anode potential from the cathode potential, and only then do the charge and mass calculations.Tutor Registration →
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