Free Reversible reactions & equilibrium questions for IGCSE Chemistry (0620), part of Chemical reactions. Each question has the answer and the marking points an examiner would look for.
Generate a full Reversible Reactions & Equilibrium worksheet →All Chemical reactions questionsCH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) ΔH is positive.
The temperature of the equilibrium mixture is increased.
What happens to the rate of the forward reaction and to the yield of the product(s) at equilibrium?
| rate | equilibrium yield | |
|---|---|---|
| A | decreases | decreases |
| B | decreases | increases |
| C | increases | decreases |
| D | increases | increases |
Answer: D
Which statement describes reversible reaction?
Answer: B
Ammonia is made in the Haber process: N₂(g) + 3H₂(g) ⇌ 2NH₃(g). The forward reaction is exothermic.
State the meaning of the symbol ⇌.
Explain the effect on the yield of ammonia of increasing the pressure.
Explain why a temperature of about 450 °C is used, even though a lower temperature gives a higher yield.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | reversible reaction reversible reaction B1 | 1 |
| (b) | yield increases; fewer gas molecules on right yield increases B1 equilibrium moves to the side with fewer gas molecules (4 → 2) B1 | 2 |
| (c) | compromise rate vs yield a lower temperature would make the rate too slow B1 450 °C is a compromise between rate and yield B1 | 2 |
Hydrated copper(II) sulfate is blue. When heated it forms white anhydrous copper(II) sulfate and water.
Write the equation for this reversible reaction.
Describe what is seen when water is added to anhydrous copper(II) sulfate.
State a use of this reaction.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | CuSO₄·5H₂O ⇌ CuSO₄ + 5H₂O correct formulae B1 reversible arrow B1 | 2 |
| (b) | white to blue, gets hot turns from white to blue B1 heat is released (it gets hot) B1 | 2 |
| (c) | test for water to test for the presence of water B1 | 1 |
Ammonia is manufactured by the Haber process.
N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = −92 kJ/mol
Typical conditions are 450 °C and 250 atmospheres with an iron catalyst.
State the sources of nitrogen and hydrogen.
Explain why a high pressure increases the equilibrium yield of ammonia.
A lower temperature would give a higher equilibrium yield. Explain why, and explain why 450 °C is used instead.
State the effect of the iron catalyst on the equilibrium yield and on the time taken to reach equilibrium.
Suggest one reason why pressures much higher than 250 atmospheres are not used.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | nitrogen: (fractional distillation of liquid) air; hydrogen: methane (natural gas) reacting with steam air B1 methane / natural gas (with steam) B1 | 2 |
| (b) | Equilibrium shifts to the side with fewer moles of gas; 2 moles on the right compared with 4 on the left fewer moles/molecules of gas on the right (2 vs 4) B1 equilibrium shifts to the right (to reduce pressure) B1 | 2 |
| (c) | Forward reaction is exothermic so lower temperature shifts equilibrium right; but rate would be too slow at low temperature, so a compromise temperature is used forward reaction is exothermic B1 lower temperature shifts the equilibrium to the right B1 rate too slow at low temperature B1 compromise between yield and rate B1 | 4 |
| (d) | No effect on yield; equilibrium reached faster no effect on the position of equilibrium / yield B1 equilibrium reached more quickly B1 | 2 |
| (e) | Expensive (energy/strong equipment) / safety risk cost of equipment/energy or safety B1 | 1 |
A reversible reaction reaches dynamic equilibrium in a closed system.
State two features of a dynamic equilibrium.
Explain why equilibrium can only be reached in a closed system.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | rates equal; concentrations constant the rates of the forward and backward reactions are equal B1 the concentrations of reactants and products stay constant B1 | 2 |
| (b) | nothing escapes so that no reactants or products can escape B1 | 1 |
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Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in