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S5 Chemistry: Rates of Reaction (Paper 4: misconception drill)
S5 Chemistry: Rates of Reaction (Paper 4: misconception drill)
Ten misconception items on a reversed formula, unconverted units, misreading the late rate, catalysts and equilibrium, mass loss and moles, comparing only final volumes, powder against lumps, doubling with temperature, catalysts and energy, and the concentration of solids.
Direct answers Answers in order: change divided by time, convert to seconds and dm3 first, fewer reactants so it slows, equilibrium position unchanged, convert to moles first, compare the times, the same total volume, the rate is multiplied by about 2, the activation energy is lowered, and solid concentration is constant.
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: Rates of Reaction |
| Level | S5 |
02 Questions (10 items)
- FoundationA student calculates rate as time divided by change. What is the correct method?
- FoundationWhich conversion is most often forgotten before a rate is calculated?
- IntermediateA student says the rate is faster late in the reaction because there is more product. What is the correct explanation?
- IntermediateA student says a catalyst shifts the equilibrium to the right. What is correct?
- ChallengeA student takes the mass lost during a reaction as the mass of reactant used. How should this be corrected?
- ChallengeWhen comparing two runs a student only compares the final gas volume. Why is that not enough?
- FoundationA student thinks powder gives more gas in total than lumps. What is correct?
- IntermediateA student treats every 10 C rise as adding 10 to the rate. What is the correct relation?
- ChallengeA student says a catalyst increases the energy of effective collisions. What is correct?
- Error redoA student says a higher concentration of a solid reactant gives a faster rate. How should a solid be described?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Rate is the change divided by the time | The change is the numerator and the time is the denominator, and reversing them gives a time unit instead of a rate. |
| 2 | Changing minutes into seconds and cm3 into dm3 | The time must be in seconds and the volume in dm3 to give the standard unit. |
| 3 | The rate slows with time because the reactant concentration falls | The rate depends on collisions between reactant particles, which become fewer as reactants are used up. |
| 4 | A catalyst only makes equilibrium arrive sooner and does not shift its position | A catalyst speeds up both directions equally, so the equilibrium concentrations are unchanged. |
| 5 | The mass lost is the mass of gas released, and it must be converted to moles before the rate is found | Convert the moles of gas into the amount of reactant consumed, then divide by the time. |
| 6 | The same final volume does not mean the same speed; the times to reach it must be compared | Rate is change over time, and the total volume alone says nothing about how long it took. |
| 7 | With the same moles the final gas volume is the same | Particle size changes only the surface area and the rate, not the total amount. |
| 8 | The rate is multiplied by about 2, not increased by adding | Three intervals of 10 C give 2 to the power 3, which is 8 times. |
| 9 | A catalyst lowers the activation energy while the energy distribution of particles is unchanged | A catalyst changes the reaction path so more particles can pass a lower barrier. |
| 10 | The concentration of a solid is constant, so the rate depends on the surface area | The concentration of a pure solid does not change, so solid reactions are compared by particle size and surface area. |
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 write the formula rate equals change divided by time first, then substitute the numbers and give the unit.Tutor Registration →
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