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S6 Chemistry: Electrochemical Cells and Fuel Cells (Paper 4: misconception drill)
S6 Chemistry: Electrochemical Cells and Fuel Cells (Paper 4: misconception drill)
Ten drill items on the sign of the anode, the silver zinc potential, the products of a fuel cell, electrons against mass of zinc, the standard temperature and pressure, the copper silver potential, electrons per hydrogen, the effect of removing the bridge, the iron zinc potential, and whether electrons cross the bridge.
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)
- FoundationIn a zinc copper cell, is the anode the positive or the negative electrode?
- FoundationWhat is the E-cell of a silver zinc cell with Ag as plus 0.80 V and Zn as minus 0.76 V?
- FoundationWhat are the products of a hydrogen oxygen fuel cell?
- IntermediateHow many grams of zinc dissolve when 0.10 mol of electrons flow, with Zn as 65.4?
- IntermediateWhat are the standard temperature and pressure for electrode potentials?
- IntermediateWhat is the E-cell of a copper silver cell?
- ChallengeHow many moles of electrons does 1 mol of hydrogen transfer in a fuel cell?
- ChallengeWhat happens to the voltage if the salt bridge is removed?
- ChallengeWhat is the E-cell of an iron zinc cell with Fe as minus 0.44 V and Zn as minus 0.76 V?
- Error redoA student thinks electrons pass through the salt bridge. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | The negative electrode | The anode is oxidised and releases electrons, so electrons leave the cell from the negative electrode. |
| 2 | 1.56 V | 0.80 minus minus 0.76 gives 1.56 V, the same method as in the second paper. |
| 3 | Water only | There is no carbon in the fuel, so no carbon dioxide forms, which is why it is cleaner. |
| 4 | 3.27 g | Two electrons dissolve one zinc, so 0.10 mol of electrons means 0.05 mol of zinc, and that times 65.4 gives 3.27 g. |
| 5 | 298 K and 100 kPa | 273 K is a common slip, but the standard temperature is 298 K. |
| 6 | 0.46 V | 0.80 minus 0.34 gives 0.46 V. |
| 7 | 2 mol | The half equation releases two electrons per molecule, so the answer is often wrongly given as one. |
| 8 | The circuit is broken and the voltage falls to zero | Without an ion path the charge builds up and stops the reaction at once. |
| 9 | 0.32 V | Zinc is the more reactive metal and the anode, so minus 0.44 minus minus 0.76 gives 0.32 V. |
| 10 | The bridge carries ions only, and electrons travel in the external circuit | If electrons could cross the solution the cell would short circuit internally and could do no external work. |
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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