Chemical Reactions | Practice Tests | Chemistry | Form 2

KASEMPA DAY SECONDARY

NATURAL SCIENCE

GRADE: Form 2 TERM: 2 YEAR: 2026

TIME: 1 HOUR 30 MINUTES TOTAL MARKS: 50

NAME OF PUPIL: ...............................................................................................

SUBJECT: CHEMISTRY

INSTRUCTIONS:

1. Answer ALL questions in the spaces provided.

2. Show all working for calculations.

3. Use correct units where applicable.

4. Marks for each question are shown in brackets.

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SECTION A: SCENARIO-BASED SHORT RESPONSE [20 MARKS] 1. Your chemistry teacher in class neutralised dilute hydrochloric acid with sodium hydroxide during a demonstration. The teacher said salt and water formed and the mixture stayed clear. (a) Write the balanced molecular equation for the reaction. Include correct state symbols in lower case in the same line with each species. [4] (b) Write the complete ionic equation for the reaction. [3] (c) Write the net ionic equation for the reaction. [2] (d) Name the spectator ion or ions in this reaction. [1] (e) Explain in one sentence why spectator ions do not appear in the net ionic equation. [0] 2. A student dropped a clean piece of zinc metal into a test-tube containing dilute sulfuric acid in the school laboratory. Bubbles of a gas formed and the zinc gradually dissolved. (a) Write the balanced molecular equation for the reaction. Include correct state symbols in lower case in the same line with each species. [4] (b) Write the full ionic equation for the reaction. [3] (c) Write the net ionic equation for the reaction. [2] (d) State the formula and the correct state symbol for the gas produced. [1] SECTION B: PRACTICAL / APPLICATION TASKS [15 MARKS] 3. At the market, a baker uses baking soda (sodium hydrogen carbonate) and vinegar (a dilute solution of ethanoic acid) when making a cake. When the two mix, bubbling occurs and a salt forms. (a) Write the balanced molecular equation for the reaction between sodium hydrogen carbonate and ethanoic acid. Include state symbols in lower case with each species. [4] (b) Write the complete ionic equation for the reaction you gave in (a). [3] (c) Identify the spectator ion or ions, if any. [2] (d) Write the net ionic equation. [3] (e) Explain in two short sentences why gas is produced during this reaction. Use simple chemical terms. [3] SECTION C: INTEGRATED STRUCTURED SCENARIO [15 MARKS] 4. During a school practical, a learner mixed two clear aqueous solutions. A white solid formed and the liquid became slightly cloudy. The teacher said a precipitation reaction had occurred. (a) Suggest two pairs of common laboratory reagents (formulas with state symbols) that could give a white precipitate when mixed. For one pair use silver nitrate and sodium chloride. For the other pair choose any suitable soluble ionic reagents. Write balanced molecular equations for both pairs. [6] (b) For the pair silver nitrate and sodium chloride used above, describe the observation the learner would make in one clear sentence. [2] (c) For the silver nitrate and sodium chloride reaction, write the full ionic equation and then the net ionic equation. Use correct state symbols. [4] (d) Name the spectator ion or ions in the silver nitrate and sodium chloride reaction. Explain in one short sentence why these ions are spectators. [3] ---------------------------- MARKING SCHEME TOTAL = 50 MARKS SECTION A: QUESTIONS 1 and 2 TOTAL 20 MARKS Question 1 (10 marks) (a) Balanced molecular equation [4] • Correct balanced formula with states: HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l) [4 marks] Marking: 2 marks for correct formulae and balance; 2 marks for correct state symbols in lower case in same line. (b) Complete ionic equation [3] • H⁺(aq) + Cl^-(aq) + Na⁺(aq) + OH^-(aq) → Na⁺(aq) + Cl^-(aq) + H₂O(l) [3 marks] Marking: 2 marks for correct ion separation and species; 1 mark for including H₂O(l) correctly (not ionised). (c) Net ionic equation [2] • H⁺(aq) + OH^-(aq) → H₂O(l) [2 marks] Marking: 2 marks for correct net ionic equation with state. (d) Spectator ion(s) [1] • Answer: Na⁺(aq) and Cl^-(aq) [1 mark] Marking: 1 mark for naming both ions or saying "Na⁺ and Cl^-". Question 2 (10 marks) (a) Balanced molecular equation [4] • Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) [4 marks] Marking: 2 marks for correct formulae and balance; 2 marks for correct state symbols. (b) Full ionic equation [3] • Zn(s) + 2H⁺(aq) + SO₄^2-(aq) → Zn²⁺(aq) + SO₄^2-(aq) + H₂(g) [3 marks] Marking: 2 marks for correct ions and species; 1 mark for correct states (aq or g). (c) Net ionic equation [2] • Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g) [2 marks] Marking: 2 marks for correct net ionic equation with states. (d) Gas formula and state [1] • H₂(g) [1 mark] Marking: 1 mark for correct formula and state. SECTION B: QUESTION 3 TOTAL 15 MARKS Question 3 (15 marks) (a) Balanced molecular equation [4] • NaHCO₃(s) + CH₃COOH(aq) → CH₃COONa(aq) + H₂O(l) + CO₂(g) [4 marks] Marking: 2 marks for correct products and balance; 2 marks for correct state symbols. (b) Complete ionic equation [3] • Na⁺(aq) + HCO₃^-(aq) + CH₃COOH(aq) → CH₃COO^-(aq) + Na⁺(aq) + H₂O(l) + CO₂(g) [3 marks] Marking: 2 marks for correct ions and molecules; 1 mark for correct states and CO₂(g) and H₂O(l). (c) Spectator ion(s) [2] • Na⁺(aq) [1 mark] — 1 mark for naming. • If student lists none or repeats, 0 marks extra. [1 additional mark for explanation if given] (d) Net ionic equation [3] • HCO₃^-(aq) + CH₃COOH(aq) → CH₃COO^-(aq) + H₂O(l) + CO₂(g) [3 marks] Marking: 2 marks for correct cancellation of Na⁺; 1 mark for correct states and CO₂(g). (e) Explanation for gas formation [3] Marking: Up to 3 marks total: • 1 mark: Acid reacts with bicarbonate to form carbonic acid. (State: H₂CO₃ forms) • 1 mark: Carbonic acid decomposes to water and carbon dioxide. • 1 mark: CO₂(g) bubbles out and is seen as effervescence. Accept concise two-sentence explanation covering these points. SECTION C: QUESTION 4 TOTAL 15 MARKS Question 4 (15 marks) (a) Two reagent pairs and balanced molecular equations [6] Marking: 3 marks for each pair (total 6). • Silver nitrate + sodium chloride pair example (3 marks): AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq) [3 marks] Marking: 2 marks for correct formulae and products; 1 mark for correct state symbols. • Second suitable pair example (3 marks), e.g.: BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq) [3 marks] Marking: 2 marks for correct formulae and products; 1 mark for correct state symbols. Accept other correct soluble reagent pairs that form white precipitate (marks awarded similarly). (b) Observation description [2] Marking: 2 marks for a clear single-sentence observation, e.g. "A white solid formed and the solution became cloudy." 1 mark for partial description (e.g., "white solid formed"). (c) Full ionic and net ionic equations for AgNO₃ + NaCl [4] Marking breakdown: • Full ionic equation [2]: Ag⁺(aq) + NO₃^-(aq) + Na⁺(aq) + Cl^-(aq) → AgCl(s) + Na⁺(aq) + NO₃^-(aq) 2 marks for correct ions and states. • Net ionic equation [2]: Ag⁺(aq) + Cl^-(aq) → AgCl(s) 2 marks for correct net ionic equation with state. (d) Spectator ions and explanation [3] Marking: • 1.5 marks for naming both spectator ions correctly: Na⁺(aq) and NO₃^-(aq). • 1.5 marks for explanation: e.g. "They remain dissolved and do not form the solid; they appear unchanged on both sides of the full ionic equation." (Clear short sentence) END OF MARKING SCHEME

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