Secondary 3 Chemistry Acids Bases Salts Quiz

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Secondary 3 Chemistry Quiz - Acids Bases Salts

Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 45

Duration: 60 Minutes
Total Marks: 45

Instructions:

• Answer all questions in the spaces provided.
• Show all working for calculation questions.
• Use a ruler for any diagrams.

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Section A: Short Answer & Concept Recall (Questions 1-8)

1. Which solid compound is commonly added to agricultural soil to increase its pH level? [1]

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2. State the two compounds that must be reacted together to produce an ammonium salt. [1]

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3. Define the term strong acid in terms of its ionisation in aqueous solution. [2]

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4. A student is testing a substance that reacts with both hydrochloric acid and sodium hydroxide solution. What is the chemical term for such a compound? [1]

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5. State the color of the precipitate formed when aqueous sodium hydroxide is added to a solution containing $\text{Cu}^{2+}$ ions. [1]

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6. Which of the following is a property of a weak alkali? [1] A) Fully dissociates in water B) Has a pH of 14 C) Partially dissociates in water D) Reacts violently with all metals

   Answer: ________

7. Name a salt that is insoluble in water. [1]

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8. State the gas evolved when dilute nitric acid reacts with calcium carbonate. [1]

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Section B: Application & Data Interpretation (Questions 9-15)

9. An amphoteric oxide, $\text{Al}_2\text{O}_3$, is known to react with both acids and bases. (a) Write a balanced chemical equation for the reaction between $\text{Al}_2\text{O}_3$ and $\text{HCl}$. [2]

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   (b) Explain why $\text{Al}_2\text{O}_3$ is described as amphoteric. [2]

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10. A student performs a titration to determine the concentration of an acid. The following results were obtained:

    • Rough: $24.50\text{ cm}^3$
    • Titration 1: $23.10\text{ cm}^3$
    • Titration 2: $23.20\text{ cm}^3$
    • Titration 3: $23.10\text{ cm}^3$ Calculate the average volume of the acid required for complete neutralisation. [2]

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11. Calculate the number of moles of $\text{H}_2\text{SO}_4$ present in $250\text{ cm}^3$ of a $0.10\text{ mol/dm}^3$ solution. [2]

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12. Compare the pH of $0.1\text{ mol/dm}^3$ hydrochloric acid and $0.1\text{ mol/dm}^3$ ethanoic acid. Which is lower? Explain your answer. [3]

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13. Describe the method used to prepare a pure, dry sample of barium sulfate. [3]

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14. A salt is prepared by reacting an excess of zinc carbonate with dilute sulfuric acid. (a) Name the salt produced. [1]

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    (b) Why is the zinc carbonate added in excess? [2]

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15. State the solubility of the following salts: [3] (a) Sodium Nitrate: ____________________ (b) Lead(II) Sulfate: ____________________ (c) Potassium Chloride: ____________________

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Section C: Extended Reasoning & Calculations (Questions 16-20)

16. A solution of an unknown organic acid contains $6.00\text{ g/dm}^3$ of the acid. If the molar concentration of the solution is $0.20\text{ mol/dm}^3$, calculate the relative molecular mass ($\text{M}_r$) of the acid. [3]

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17. Explain the difference between a "concentrated acid" and a "strong acid". [3]

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18. A student wants to prepare a sample of lead(II) nitrate. (a) Suggest the most suitable reactants. [2]

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    (b) Describe the steps to obtain the salt in pure, crystalline form. [3]

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19. Write balanced chemical equations (including state symbols) for the following: [4] (a) Magnesium reacting with dilute nitric acid.

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    (b) Sodium hydroxide reacting with ammonium chloride.

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20. An unknown salt $X$ is soluble in water. When aqueous sodium hydroxide is added, a white precipitate is formed which dissolves in excess sodium hydroxide. When aqueous ammonia is added, a white precipitate is formed which does NOT dissolve in excess ammonia. Identify the cation present in salt $X$. [3]

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Secondary 3 Chemistry Quiz - Acids Bases Salts (Answers)

1. Calcium oxide ($\text{CaO}$) / Calcium hydroxide ($\text{Ca(OH)}_2$) / Calcium carbonate ($\text{CaCO}_3$). [1]

2. Ammonia (or ammonium hydroxide) and an acid. [1]

3. An acid that completely ionises/dissociates in aqueous solution to produce $\text{H}^+$ ions. [2]

4. Amphoteric. [1]

5. Light blue. [1]

6. C) Partially dissociates in water. [1]

7. $\text{AgCl}$ / $\text{BaSO}_4$ / $\text{PbSO}_4$ / $\text{CaCO}_3$ (Any one valid). [1]

8. Carbon dioxide ($\text{CO}_2$). [1]

9. (a) $\text{Al}_2\text{O}_3(\text{s}) + 6\text{HCl}(\text{aq}) \rightarrow 2\text{AlCl}_3(\text{aq}) + 3\text{H}_2\text{O}(\text{l})$ [2] (b) It reacts with both strong acids and strong alkalis. [2]

10. Concordant results are $23.10$ and $23.20$ and $23.10$. Average = $(23.10 + 23.20 + 23.10) / 3 = 23.13\text{ cm}^3$ (or $23.1\text{ cm}^3$ if only taking the two closest). [2]

11. $\text{n} = \text{c} \times \text{V} = 0.10\text{ mol/dm}^3 \times (250/1000)\text{ dm}^3 = 0.025\text{ mol}$. [2]

12. Hydrochloric acid has a lower pH. [1] $\text{HCl}$ is a strong acid and fully ionises in water, [1] whereas ethanoic acid is a weak acid and only partially ionises, resulting in a lower concentration of $\text{H}^+$ ions. [1]

13. Precipitation method. [1] Mix barium nitrate and sodium sulfate solutions. [1] Filter the precipitate, wash with distilled water, and dry between filter papers. [1]

14. (a) Zinc sulfate. [1] (b) To ensure all the sulfuric acid is completely neutralised. [2]

15. (a) Soluble [1] (b) Insoluble [1] (c) Soluble [1]

16. $\text{M}_r = \text{mass concentration} / \text{molar concentration}$ $\text{M}_r = 6.00\text{ g/dm}^3 / 0.20\text{ mol/dm}^3 = 30\text{ g/mol}$. [3]

17. Strong acid refers to the extent of ionisation (complete vs partial). [1] Concentrated acid refers to the amount of acid solute dissolved in a given volume of solvent. [1] A concentrated acid can be weak (e.g., concentrated ethanoic acid). [1]

18. (a) Lead(II) oxide (or carbonate) and dilute nitric acid. [2] (b) Heat the mixture, filter off excess base, evaporate the filtrate to saturation point, cool to crystallise, filter and dry. [3]

19. (a) $\text{Mg}(\text{s}) + 2\text{HNO}_3(\text{aq}) \rightarrow \text{Mg}(\text{NO}_3)_2(\text{aq}) + \text{H}_2(\text{g})$ [2] (b) $\text{NaOH}(\text{aq}) + \text{NH}_4\text{Cl}(\text{s/aq}) \rightarrow \text{NaCl}(\text{aq}) + \text{NH}_3(\text{g}) + \text{H}_2\text{O}(\text{l})$ [2]

20. The cation is $\text{Al}^{3+}$. [1] White ppt with $\text{NaOH}$ that dissolves in excess indicates $\text{Al}^{3+}$ or $\text{Zn}^{2+}$. [1] The fact that it does NOT dissolve in excess ammonia distinguishes it from $\text{Zn}^{2+}$. [1]