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Secondary 3 Chemistry Acids Bases Salts Quiz

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Questions

Secondary 3 Chemistry Quiz - Acids Bases Salts

Name: __________________________
Class: __________________________
Date: __________________________
Score: _______ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

Answer all questions.
Write your answers in the spaces provided.
Show all working for calculation questions.
The number of marks is indicated in brackets [ ] at the end of each question or part question.

Section A: Multiple Choice & Short Answer (10 Marks)

1. Which substance, when added to soil, will increase the pH of acidic soil? [1]
A. Ammonium nitrate
B. Calcium hydroxide
C. Sodium chloride
D. Sulfuric acid

Answer: __________________________

2. Which pair of compounds reacts to form an ammonium salt? [1]
A. Ammonia and sodium hydroxide
B. Ammonia and nitric acid
C. Ammonium chloride and water
D. Nitrogen and hydrogen

Answer: __________________________

3. A student tests an unknown solution with universal indicator. The indicator turns red. Which statement is correct? [1]
A. The solution is a strong alkali.
B. The solution is a weak alkali.
C. The solution is a strong acid.
D. The solution is neutral.

Answer: __________________________

4. Which oxide is amphoteric? [1]
A. Calcium oxide
B. Carbon dioxide
C. Sodium oxide
D. Zinc oxide

Answer: __________________________

5. What is the definition of a monatomic gas? [1]

6. State the colour of universal indicator in a solution with pH 13. [1]

7. Complete the following word equation for the reaction between a metal carbonate and an acid. [2]
Metal carbonate + Acid $\rightarrow$ _______________ + _______________ + Carbon dioxide

8. Why is barium sulfate used in medicine for X-rays of the digestive system, despite barium ions being toxic? [1]

9. Which gas is produced when zinc reacts with dilute hydrochloric acid? [1]
A. Oxygen
B. Hydrogen
C. Carbon dioxide
D. Chlorine

Answer: __________________________

10. What is the pH of a neutral solution at room temperature? [1]

Section B: Structured Questions (20 Marks)

11. A student carries out a titration to determine the concentration of sulfuric acid using aqueous sodium hydroxide.
The equation for the reaction is:
$2NaOH(aq) + H_2SO_4(aq) \rightarrow Na_2SO_4(aq) + 2H_2O(l)$

The student performs a rough titration followed by three accurate titrations. The results are shown below:

Titration	Rough	1	2	3
Final burette reading / cm³	24.50	23.80	47.60	24.10
Initial burette reading / cm³	0.00	0.00	23.80	0.20
Volume of acid used / cm³	24.50	23.80	23.80	23.90

(a) Identify the concordant results. [1]

(b) Calculate the average volume of sulfuric acid used. [1]

(c) The concentration of the sodium hydroxide solution is $0.10 \text{ mol/dm}^3$ . $25.0 \text{ cm}^3$ of sodium hydroxide was used in each titration.
Calculate the number of moles of sodium hydroxide in $25.0 \text{ cm}^3$ . [2]
<br> <br> <br>

(d) Using your answer to (c) and the mole ratio from the equation, calculate the number of moles of sulfuric acid that reacted. [1]
<br> <br>

(e) Calculate the concentration of the sulfuric acid in $\text{mol/dm}^3$ . [2]
<br> <br> <br>

12. Zinc oxide is an amphoteric oxide.
(a) Define the term amphoteric. [1]

(b) Write a balanced chemical equation for the reaction between zinc oxide and dilute hydrochloric acid. [2]
<br> <br>

(c) Write a balanced chemical equation for the reaction between zinc oxide and aqueous sodium hydroxide. (Note: Sodium zincate, $Na_2ZnO_2$ , is formed). [2]
<br> <br>

13. Salts can be prepared by different methods.
(a) Name the method used to prepare insoluble lead(II) sulfate from aqueous lead(II) nitrate and dilute sulfuric acid. [1]

(b) Describe the essential steps to obtain a pure, dry sample of lead(II) sulfate using the method named in (a). [3]

(c) Why cannot copper(II) sulfate be prepared by reacting copper metal with dilute sulfuric acid? [1]

14. The table below shows the pH values of four different solutions, A, B, C, and D.

Solution	pH
A	1
B	6
C	13
D	7

(a) Which solution is a strong acid? [1]

(b) Which solution is neutral? [1]

(c) Solution B is ethanoic acid (a weak acid) and Solution A is hydrochloric acid (a strong acid). Both have the same concentration ( $0.1 \text{ mol/dm}^3$ ).
Explain, in terms of ionisation, why the pH of ethanoic acid is higher than that of hydrochloric acid. [2]

15. Ammonia is manufactured industrially by the Haber Process.
$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \quad \Delta H = -92 \text{ kJ/mol}$

(a) State the catalyst used in the Haber Process. [1]

(b) Ammonia is used to make fertilisers. Name one ammonium salt commonly used as a fertiliser. [1]

(c) Ammonium salts react with bases to release ammonia gas.
Describe the test for ammonia gas, including the observation. [2]

(d) A farmer adds calcium hydroxide to soil to reduce acidity. Explain why ammonium sulfate fertiliser should not be added to the soil at the same time. [2]

Section C: Application & Analysis (10 Marks)

16. A student wants to prepare crystals of copper(II) sulfate from copper(II) oxide and dilute sulfuric acid.
(a) Why is excess copper(II) oxide added to the acid? [1]

(b) How is the excess copper(II) oxide removed? [1]

(c) Describe how dry crystals of copper(II) sulfate are obtained from the filtrate. [2]

17. Consider the reaction between magnesium and hydrochloric acid:
$Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)$

(a) Describe the observation when magnesium ribbon is added to excess dilute hydrochloric acid. [2]

(b) If the experiment is repeated using ethanoic acid of the same concentration, the reaction is slower. Explain why. [2]

18. Sodium hydroxide solution is added dropwise to a solution containing iron(II) ions ( $Fe^{2+}$ ).
(a) State the colour of the precipitate formed. [1]

(b) Write the ionic equation for this reaction. [2]
<br> <br>

19. Dilute nitric acid is added to a solution of potassium carbonate.
(a) Write the balanced chemical equation for this reaction. [2]
<br> <br>

(b) Describe the test for the gas produced, including the observation. [2]

20. Explain why aluminium oxide is considered amphoteric, but magnesium oxide is considered basic only. Include reference to their reactions with acids and alkalis. [4]

Answers

Secondary 3 Chemistry Quiz - Acids Bases Salts (Answer Key)

Total Marks: 40

Section A: Multiple Choice & Short Answer

1. B [1]
Calcium hydroxide (slaked lime) is a base used to neutralise acidic soil.

2. B [1]
Ammonia (base) + Nitric acid (acid) $\rightarrow$ Ammonium nitrate (salt).

3. C [1]
Red indicates a strongly acidic solution (pH 1-2).

4. D [1]
Zinc oxide reacts with both acids and bases.

5. Consisting of single atoms (not bonded to other atoms). [1]
Example: Noble gases like Helium.

6. Purple / Violet [1]

7. Salt + Water [2]
(1 mark for Salt, 1 mark for Water)

8. Barium sulfate is insoluble. [1]
Therefore, toxic barium ions are not released into the body.

9. B [1]
Metal + Acid $\rightarrow$ Salt + Hydrogen.

10. 7 [1]

Section B: Structured Questions

11. Titration Calculations

(a) Titration 1 and Titration 2 (23.80 cm³ and 23.80 cm³). [1]
Note: Titration 3 (23.90) is within 0.10 cm³ of 1 and 2, so 1, 2, and 3 are concordant. Accept 1 & 2 OR 1, 2 & 3.

(b) Average volume = $\frac{23.80 + 23.80 + 23.90}{3} = 23.83 \text{ cm}^3$ [1]
(If student used only 1 & 2: 23.80 cm³. Accept either if reasoning is clear. Standard answer key uses all concordant: 23.83 cm³)

(c) Moles of NaOH = $C \times V$
$V = 25.0 \text{ cm}^3 = 0.025 \text{ dm}^3$
$n = 0.10 \times 0.025 = 0.0025 \text{ mol}$ [2]
(1 mark for conversion/formula, 1 mark for answer)

(d) Mole ratio NaOH : $H_2SO_4$ is 2 : 1.
Moles of $H_2SO_4$ = $\frac{0.0025}{2} = 0.00125 \text{ mol}$ [1]

(e) Concentration of $H_2SO_4$ = $\frac{n}{V}$
$V_{acid} = 23.83 \text{ cm}^3 = 0.02383 \text{ dm}^3$
$C = \frac{0.00125}{0.02383} \approx 0.0525 \text{ mol/dm}^3$ [2]
(1 mark for substitution, 1 mark for answer with units. Accept 0.052 - 0.053)

12. Amphoteric Oxides

(a) An oxide that reacts with both acids and bases to form a salt and water. [1]

(b) $ZnO(s) + 2HCl(aq) \rightarrow ZnCl_2(aq) + H_2O(l)$ [2]
(1 mark for correct formulas, 1 mark for balancing)

(c) $ZnO(s) + 2NaOH(aq) \rightarrow Na_2ZnO_2(aq) + H_2O(l)$ [2]
(1 mark for correct formulas, 1 mark for balancing)

13. Salt Preparation

(a) Precipitation [1]

(b)

Mix aqueous lead(II) nitrate and dilute sulfuric acid. [1]
Filter the mixture to collect the residue (precipitate). [1]
Wash the residue with distilled water and dry between filter papers/in an oven. [1]

(c) Copper is below hydrogen in the reactivity series. [1]
Therefore, it does not react with dilute acids to release hydrogen/displace hydrogen.

14. pH and Strength

(a) Solution A [1]

(b) Solution D [1]

(c)

Strong acids (HCl) ionise completely in water. [1]
Weak acids (Ethanoic acid) ionise only partially in water. [1]
Therefore, [H+] concentration is lower in ethanoic acid, resulting in a higher pH.

15. Ammonia and Fertilisers

(a) Iron [1]

(b) Ammonium nitrate / Ammonium sulfate / Ammonium phosphate [1]
(Any correct ammonium salt)

(c)

Test: Use damp red litmus paper. [1]
Observation: The paper turns blue. [1]

(d)

Calcium hydroxide is a base/alkali. [1]
It will react with ammonium sulfate to release ammonia gas, causing loss of nitrogen from the fertiliser. [1]
Equation support: $(NH_4)_2SO_4 + Ca(OH)_2 \rightarrow CaSO_4 + 2H_2O + 2NH_3$

Section C: Application & Analysis

16. Preparation of Copper(II) Sulfate

(a) To ensure all the acid reacts / to ensure the salt formed is pure (no acid remaining). [1]

(b) Filtration. [1]

(c)

Heat the filtrate to evaporate some water / until saturation point (crystallisation point). [1]
Allow to cool slowly to form crystals, then filter and dry. [1]

17. Reaction Rates and Acids

(a)

Effervescence / Bubbles of gas produced. [1]
Magnesium ribbon disappears / dissolves. [1]

(b)

Ethanoic acid is a weak acid and partially ionised, so the concentration of $H^+$ ions is lower. [1]
Lower frequency of effective collisions between $H^+$ ions and Mg atoms. [1]

18. Precipitation Reactions

(a) Green precipitate. [1]

(b) $Fe^{2+}(aq) + 2OH^-(aq) \rightarrow Fe(OH)_2(s)$ [2]
(1 mark for correct formulas and state symbols, 1 mark for balancing)

19. Carbonates and Acids

(a) $K_2CO_3(aq) + 2HNO_3(aq) \rightarrow 2KNO_3(aq) + H_2O(l) + CO_2(g)$ [2]
(1 mark for correct formulas, 1 mark for balancing)

(b)

Test: Bubble the gas through limewater (calcium hydroxide solution). [1]
Observation: Limewater turns milky / cloudy. [1]

20. Oxide Classification

Aluminium oxide reacts with acids to form salt and water (acting as a base). [1]
Aluminium oxide reacts with alkalis (bases) to form salt and water (acting as an acid). [1]
Therefore, it is amphoteric. [1]
Magnesium oxide reacts with acids to form salt and water, but does not react with alkalis. [1]
Therefore, it is basic only.