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S5 Chemistry: Chemical Equilibrium and Le Chatelier Principle (Paper 4: Misconception Drill)
S5 Chemistry: Chemical Equilibrium and Le Chatelier Principle (Paper 4: Misconception Drill)
Ten items targeting the commonest equilibrium misconceptions about Kc, catalysts and pressure or temperature changes.
Direct answers Answers in order: no, no, no, Kc falls and shifts left, no, it increases, no, dimensionless, reverse, no.
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 Equilibrium and Le Chatelier Principle |
| Level | S5 |
02 Questions (10 items)
- FoundationDrill: should pure solids and pure liquids appear in the Kc expression?
- FoundationDrill: are all concentrations equal at equilibrium?
- FoundationDrill: does a catalyst change Kc?
- IntermediateDrill: how does raising the temperature affect Kc of an exothermic reaction?
- IntermediateDrill: does raising the pressure shift H2(g) + I2(g) ⇌ 2HI(g)?
- IntermediateDrill: what happens to the amount of CO2 when the pressure on CaCO3(s) ⇌ CaO(s) + CO2(g) is lowered?
- ChallengeDrill: does adding an inert gas at constant volume shift an equilibrium?
- ChallengeDrill: if the gas moles are equal on both sides, does Kc have units?
- ChallengeDrill: which way does a reaction go when Q is greater than Kc?
- Error redoDrill: does a very large Kc mean the reaction is fast?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | No, only gases and species in aqueous solution are written | Pure solids and liquids have fixed concentrations already built into the constant. |
| 2 | No, equilibrium only requires Q to equal Kc | At equilibrium the ratio matches Kc, but the individual concentrations can differ widely. |
| 3 | No, it only shortens the time taken to reach equilibrium | A catalyst lowers both activation energies, leaving Kc and the position of equilibrium unchanged. |
| 4 | Kc decreases and the equilibrium shifts left | Heating favours the endothermic direction, so the exothermic forward reaction is suppressed. |
| 5 | No, both sides have the same number of gas moles so Q is unchanged | When all concentrations change by the same factor and the gas moles match, Q stays the same. |
| 6 | It increases because the equilibrium shifts right | Lowering the pressure shifts the system towards more gas moles, which is the CO2 side. |
| 7 | No, the partial pressures of the reactants do not change | Total pressure rises but partial pressures and concentrations stay the same, so there is no shift. |
| 8 | No, it is dimensionless | The concentration powers cancel, so Kc is a pure number. |
| 9 | In the reverse direction until Q equals Kc | Too much product means the reverse reaction runs until Q falls back to Kc. |
| 10 | No, Kc describes the position of equilibrium, not the rate | Rate depends on activation energy and concentration, not on the size of Kc. |
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.
Turn every wrong item today into one sentence: I thought this, but actually that.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.