Secondary 4 Pure Chemistry Acids Bases Salts Quiz

Secondary 4 Pure Chemistry Quiz - Acids Bases Salts

Name: _________________ Class: _________ Date: _____________

Score: ______ / 35 marks Duration: 45 minutes

Instructions:

• Answer all questions in the spaces provided
• Show all working for calculations
• Use appropriate chemical formulae and state symbols where required
• Write clearly and concisely

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Section A: Short Answer Questions [15 marks]

1. Sulfur dioxide gas contributes to acid rain formation. (a) Write a balanced chemical equation for the formation of sulfur dioxide from sulfur. [1]

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(b) Name the acid formed when sulfur dioxide dissolves in rainwater. [1]

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2. Complete the following word equation: [1]

Zinc + Hydrochloric acid → _________________ + _________________

3. State the colour change observed when universal indicator is added to: (a) Dilute hydrochloric acid [1]

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(b) Sodium hydroxide solution [1]

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4. A student wants to prepare copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid. (a) Write a balanced chemical equation for this reaction. [2]

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(b) State one observation during this reaction. [1]

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5. Ammonia gas can react with hydrochloric acid gas to form a white solid. (a) Name the white solid formed. [1]

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(b) Write a balanced chemical equation for this reaction. [2]

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6. State the solubility of the following salts in water: [4] (a) Sodium chloride: _________________ (b) Lead(II) chloride: _________________ (c) Silver nitrate: _________________ (d) Barium sulfate: _________________

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Section B: Structured Questions [20 marks]

7. A student investigates the reactions of different metals with dilute hydrochloric acid.

(a) The student wants to prepare zinc chloride by reacting zinc with dilute hydrochloric acid.

(i) Write a balanced chemical equation for this reaction. [2]

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(ii) State two observations the student would make during this reaction. [2]

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(b) The student considers using potassium instead of zinc to prepare potassium chloride.

Discuss the suitability of reacting potassium with dilute hydrochloric acid to obtain potassium chloride. [3]

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(c) Describe a simple chemical test to differentiate between zinc chloride solution and copper(II) chloride solution. Include the expected observations. [3]

Test: ____________________________________________________________

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Observation with zinc chloride: ___________________________________

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Observation with copper(II) chloride: ______________________________

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8. The diagram shows the setup for preparing a dry sample of ammonia gas.

[Assume diagram shows: CaO + (NH₄)₂SO₄ → heat → collection tube with drying agent]

(a) Name a suitable drying agent for ammonia gas. [1]

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(b) Explain why calcium oxide is mixed with ammonium sulfate. [2]

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(c) Ammonia gas can react with sulfuric acid to form ammonium sulfate.

(i) Write a balanced chemical equation for this reaction. [2]

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(ii) Calculate the maximum mass of ammonium sulfate that can be formed from 3.4 g of ammonia gas. [Relative atomic masses: N = 14, H = 1, S = 32, O = 16] [3]

Working:

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Answer: _________________ g

(d) State one large-scale use of ammonia. [1]

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Secondary 4 Pure Chemistry Quiz - Acids Bases Salts (Answer Key)

Total: 35 marks

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Section A: Short Answer Questions [15 marks]

1. (a) S + O₂ → SO₂ [1 mark] Accept: S(s) + O₂(g) → SO₂(g)

(b) Sulfurous acid / H₂SO₃ [1 mark]

2. Zinc chloride + Hydrogen [1 mark] Accept: ZnCl₂ + H₂

3. (a) Red [1 mark] (b) Blue/Purple [1 mark]

4. (a) CuO + H₂SO₄ → CuSO₄ + H₂O [2 marks] 1 mark for correct reactants and products, 1 mark for balancing

(b) Blue solution formed / Black solid dissolves / Effervescence stops [1 mark] Accept any reasonable observation

5. (a) Ammonium chloride [1 mark] Accept: NH₄Cl

(b) NH₃ + HCl → NH₄Cl [2 marks] 1 mark for correct formula, 1 mark for balancing

6. [4 marks - 1 mark each] (a) Soluble (b) Insoluble / Slightly soluble (c) Soluble
(d) Insoluble

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Section B: Structured Questions [20 marks]

7. (a)(i) Zn + 2HCl → ZnCl₂ + H₂ [2 marks] 1 mark for correct formula, 1 mark for balancing

(a)(ii) [2 marks - 1 mark each]

1. Effervescence / Bubbles of gas produced
2. Metal dissolves / Zinc disappears Accept: Heat released, colourless gas produced

(b) [3 marks]

• Potassium is very reactive / high in reactivity series [1]
• Reaction would be violent / explosive / uncontrolled [1]
• Unsuitable due to safety hazards / difficult to control [1] Accept: Too much heat released, dangerous

(c) [3 marks] Test: Add sodium hydroxide solution / Add NaOH(aq) [1]

Zinc chloride: White precipitate forms / Zn(OH)₂ precipitate / White precipitate dissolves in excess NaOH [1]

Copper(II) chloride: Blue precipitate forms / Cu(OH)₂ precipitate / Blue precipitate does not dissolve in excess NaOH [1]

8. (a) Calcium oxide / CaO / Quicklime [1 mark] Accept: Concentrated sulfuric acid (but less suitable for ammonia)

(b) [2 marks]

• Calcium oxide is a base / alkali [1]
• It reacts with ammonium sulfate to release ammonia gas [1] Accept: CaO + (NH₄)₂SO₄ → NH₃ + other products

(c)(i) 2NH₃ + H₂SO₄ → (NH₄)₂SO₄ [2 marks] 1 mark for correct formula, 1 mark for balancing

(c)(ii) [3 marks] Working:

• Moles of NH₃ = 3.4 ÷ 17 = 0.2 mol [1]
• Molar ratio NH₃ : (NH₄)₂SO₄ = 2 : 1 [1]
• Moles of (NH₄)₂SO₄ = 0.2 ÷ 2 = 0.1 mol
• Mr of (NH₄)₂SO₄ = 2(14) + 8(1) + 32 + 4(16) = 132
• Mass = 0.1 × 132 = 13.2 g [1]

Answer: 13.2 g

(d) Manufacture of fertilizers / Haber process / Making nitric acid [1 mark] Accept: Cleaning agent, refrigerant

Marking Notes:

• Award marks for correct chemical formulae even if state symbols are omitted
• Accept alternative correct methods for calculations
• Be lenient with spelling of chemical names if meaning is clear
• For equation balancing, award full marks only if completely correct