1. 1
   A swimming pool attendant tests a sample of pool water with universal indicator solution. The indicator turns orange, and a pH meter confirms a reading of pH 4. The attendant then adds small amounts of sodium hydroxide solution to bring the pH back towards 7.

   (a)

   Which ion is responsible for making the pool water acidic before the sodium hydroxide is added?

   [1 mark]

   • AH+(aq) ions
   • BOH-(aq) ions
   • CCl-(aq) ions
   • DNa+(aq) ions

   (b)

   When the pH meter finally reads exactly 7, after enough sodium hydroxide has been added, what has happened to the pool water?

   [1 mark]

   • AIt has been partially neutralised
   • BIt has been completely neutralised
   • CIt has been oxidised
   • DIt has been electrolysed

   (c)

   Write the ionic equation for the reaction taking place as the sodium hydroxide is added, and explain what this equation shows about neutralisation reactions in general.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student is given three separate acids, hydrochloric acid, nitric acid and sulfuric acid, and reacts each one separately with potassium hydroxide solution until each mixture is exactly neutral.

   (a)

   Which salt is produced when potassium hydroxide reacts with hydrochloric acid?

   [1 mark]

   • APotassium sulfate
   • BPotassium nitrate
   • CPotassium chloride
   • DPotassium oxide

   (b)

   Which salt is produced when potassium hydroxide reacts with sulfuric acid?

   [1 mark]

   • APotassium chloride
   • BPotassium nitrate
   • CPotassium hydroxide
   • DPotassium sulfate

   (c)

   The student also reacts the same potassium hydroxide with nitric acid. Name the salt produced, and explain why a different acid produces a different salt from the same base.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A pottery glaze manufacturer wants to produce a bright yellow pigment, lead chromate (an insoluble salt), for use in ceramic glazes, starting from lead nitrate solution and potassium chromate solution.

   (a)

   Describe how the manufacturer could prepare a pure, dry sample of solid lead chromate in the laboratory, starting from lead nitrate solution and potassium chromate solution.

   [3 marks]

   (b)

   Explain, using ideas about solubility, why mixing lead nitrate solution with potassium chromate solution produces a precipitate, and suggest one other pair of soluble salt solutions the manufacturer could use to make the same insoluble product, giving a reason for your choice.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A jewellery-plating company wants to produce two different products in the laboratory: a batch of pure copper sulfate crystals for use as a plating solution, and a sample of insoluble calcium sulfate to test as a filler material, using the method appropriate to each type of salt.

   (a)

   Describe, step by step, how a technician could prepare pure, dry crystals of copper sulfate starting from copper(II) oxide (an insoluble base) and dilute sulfuric acid, including how to know when the reaction is complete and how to obtain the crystals.

   [6 marks]

   (b)

   Explain why using excess copper(II) oxide, rather than excess dilute sulfuric acid, is the correct approach for this preparation, and describe how the technician should then prepare a sample of insoluble calcium sulfate for the filler material, starting from two suitable soluble salt solutions.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A gardener notices that carbon dioxide from a greenhouse heater is slowly turning a stored container of limewater cloudy. Meanwhile, a bag of ammonium sulfate fertiliser stored nearby was made by reacting ammonia solution with dilute sulfuric acid.

   (a)

   What causes the limewater to turn cloudy when carbon dioxide is bubbled through it?

   [1 mark]

   • ACalcium hydroxide dissolving
   • BCalcium carbonate forming
   • CCalcium oxide forming
   • DHydrogen gas escaping

   (b)

   What type of solution is formed when ammonia gas dissolves in water?

   [1 mark]

   • AAn alkaline solution
   • BA neutral solution
   • CAn acidic solution
   • DA colloidal suspension

   (c)

   State the general term for the type of substance ammonia is behaving as when it dissolves in water, and explain why ammonium sulfate fertiliser is described as a salt.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A fertiliser company produces three separate batches of salt by reacting sodium hydroxide solution separately with hydrochloric acid, nitric acid and sulfuric acid.

   (a)

   Which salt is produced when sodium hydroxide reacts with nitric acid?

   [1 mark]

   • ASodium chloride
   • BSodium sulfate
   • CSodium hydroxide
   • DSodium nitrate

   (b)

   Which salt is produced when sodium hydroxide reacts with sulfuric acid?

   [1 mark]

   • ASodium chloride
   • BSodium nitrate
   • CSodium sulfate
   • DSodium oxide

   (c)

   The company also reacts sodium hydroxide with hydrochloric acid. Name the salt formed, and state which type of ion in the acid determines the identity of the salt produced.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A student is given four unlabelled colourless solutions, W, X, Y and Z, and tests each with universal indicator. Solution W turns red, X turns green, Y turns purple, and Z turns orange.

   (a)

   State the approximate pH and whether each solution, W and Y, is acidic, neutral or alkaline, based on the universal indicator colours observed.

   [3 marks]

   (b)

   Solution X (green) is later found to be neutral. Explain how the student could confirm this using a pH meter instead of universal indicator, and describe how the student could then convert solution W into a neutral solution using solution Y, explaining what type of reaction would be taking place.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A laboratory technician needs to prepare two products: a solid sample of magnesium sulfate crystals (a soluble salt made from an insoluble base), and a pure solution of ammonium chloride (a soluble salt made by neutralising an alkali with an acid), using the method appropriate to each.

   (a)

   Describe, step by step, how the technician should prepare pure, dry magnesium sulfate crystals from magnesium oxide (an insoluble base) and dilute sulfuric acid.

   [6 marks]

   (b)

   The technician also needs to prepare a solution of pure ammonium chloride by reacting ammonia solution with dilute hydrochloric acid, using an indicator to know when the reaction is exactly complete. Describe how this could be done, and explain why using an indicator in this way would not be suitable if the technician wanted to produce pure, dry ammonium chloride crystals rather than just the solution.

   [6 marks]

   Total for question 8: 12 marks

End of questions