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S5 Chemistry: Chemical Cells and Fuel Cells (Paper 1: basics)
S5 Chemistry: Chemical Cells and Fuel Cells (Paper 1: basics)
Ten basic items on the negative electrode and electron flow of a zinc-copper cell, the emf of dry cells in series, the products and moles in a hydrogen-oxygen fuel cell, charge passed and the green advantage of fuel cells.
Direct answers Answers in order: zinc is negative, electrons flow from zinc to copper, 6.0 V, 18 g, 24 dm3, 572 kJ, 3600 C, 3.10 V, the only product is water, and electrons cannot pass through the solution.
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: Chemical Cells and Fuel Cells |
| Level | S5 |
02 Questions (10 items)
- FoundationIn a simple zinc-copper chemical cell, which metal is the negative electrode?
- FoundationWhen a zinc-copper cell discharges, which way do electrons flow in the external circuit?
- FoundationA dry cell has an electromotive force of 1.5 V. What is the total emf of four cells in series?
- IntermediateThe overall reaction of a hydrogen-oxygen fuel cell is 2H2 + O2 to 2H2O. What mass of water is formed from 1 mol of hydrogen?
- IntermediateHow many dm3 of oxygen are needed for 2 mol of hydrogen at room conditions, molar volume 24 dm3/mol?
- IntermediateEach mole of hydrogen releases 286 kJ in a fuel cell. How much energy do 2 mol release?
- ChallengeA cell discharges steadily at 0.50 A for 2.0 hours. What charge passes through the circuit?
- ChallengeA silver oxide button cell for a watch is 1.55 V. What is the total emf of two in series?
- ChallengeWhy is a hydrogen-oxygen fuel cell considered a greener choice than a dry cell?
- Error redoA student claims that electrons travel through the electrolyte from the negative to the positive electrode. Why is this wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Zinc is the negative electrode | Zinc is more reactive than copper and loses electrons more easily, so zinc is negative. |
| 2 | From the zinc electrode to the copper electrode | The negative electrode releases electrons and they travel through the external circuit to the positive copper electrode. |
| 3 | 6.0 V | In series the emfs add up, so 1.5 times 4 gives 6.0 V. |
| 4 | 18 g | One mole of hydrogen gives one mole of water, and the relative molecular mass of water is 18. |
| 5 | 24 dm3 | Two moles of hydrogen need one mole of oxygen, and 1 times 24 gives 24 dm3. |
| 6 | 572 kJ | Energy is proportional to moles, so 286 times 2 gives 572 kJ. |
| 7 | 3600 C | Using Q equals I times t with the time in seconds, 0.50 times 7200 gives 3600 C. |
| 8 | 3.10 V | Emfs add in series, so 1.55 times 2 gives 3.10 V. |
| 9 | Its only product is water, so no carbon dioxide is emitted | The only product of a hydrogen-oxygen fuel cell is water, so no greenhouse gas is produced. |
| 10 | Electrons cannot pass through the solution, which conducts by ion movement | Electrons travel only in the external circuit, while ions move towards the two electrodes inside the solution to complete the circuit. |
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.
For every item state the direction of electron transfer or the formula first, then substitute the numbers and give the unit.Tutor Registration →
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