1. 1
   A student wants to make copper sulfate crystals. They add copper oxide powder to warm dilute sulfuric acid a little at a time, stirring after each addition, until some unreacted black powder remains at the bottom of the beaker.

   (a)

   A student wants to make copper sulfate crystals by reacting dilute sulfuric acid with copper oxide powder, adding the powder until it is in excess. Which type of substance is copper oxide in this reaction?

   [1 mark]

   • AAn insoluble base
   • BA soluble alkali
   • CAn indicator
   • DA neutral salt

   (b)

   How does the student know that all of the sulfuric acid has reacted and no more copper oxide will dissolve?

   [1 mark]

   • AUnreacted black copper oxide powder remains undissolved at the bottom of the beaker
   • BThe mixture turns universal indicator green
   • CThe mixture starts to bubble vigorously
   • DThe mixture becomes hot to the touch

   (c)

   Describe how the student should separate the excess unreacted copper oxide from the copper sulfate solution.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A different student makes sodium chloride solution by adding a few drops of indicator to sodium hydroxide solution, then adding dilute hydrochloric acid from a burette until the indicator just changes colour, showing the solution is neutral.

   (a)

   A different student makes sodium chloride solution by reacting sodium hydroxide solution with hydrochloric acid, adding a few drops of indicator to the sodium hydroxide first. Why must an indicator be used for this reaction, unlike the copper oxide reaction?

   [1 mark]

   • ABecause both the alkali and the acid are soluble, so there is no leftover solid to show the reaction is complete
   • BBecause sodium chloride is an insoluble salt
   • CBecause hydrochloric acid does not react with sodium hydroxide
   • DBecause indicators speed up the reaction

   (b)

   Once the indicator shows the solution is exactly neutral, what must the student do before crystallising a pure sample of sodium chloride?

   [1 mark]

   • ARepeat the experiment without the indicator, using the same volumes of acid and alkali, to avoid contaminating the salt with indicator
   • BAdd more hydrochloric acid to make sure all the sodium hydroxide has reacted
   • CFilter the mixture to remove excess solid
   • DAdd more sodium hydroxide to neutralise the indicator

   (c)

   Explain why the indicator is needed during this reaction, and how the student uses it to know the reaction is complete.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A third student makes magnesium sulfate crystals by reacting magnesium ribbon with dilute sulfuric acid, filtering off the excess metal, and then needs to obtain solid crystals of the salt from the resulting solution.

   (a)

   A third student makes magnesium sulfate crystals by adding magnesium ribbon to dilute sulfuric acid until some metal remains unreacted. Describe how the student carries out this reaction safely and knows when it is complete.

   [3 marks]

   (b)

   Describe how the student obtains solid magnesium sulfate crystals from the filtered magnesium sulfate solution.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A teacher asks two students to each prepare a named soluble salt using different methods. Student X must prepare potassium sulfate crystals from potassium hydroxide and dilute sulfuric acid. Student Y must prepare zinc sulfate crystals from zinc metal and dilute sulfuric acid.

   (a)

   Describe, in full, a suitable method Student X should follow, including how to obtain pure dry crystals.

   [6 marks]

   (b)

   Describe, in full, a suitable method Student Y should follow to prepare zinc sulfate crystals from zinc metal and dilute sulfuric acid, and explain why this method does not require the use of an indicator, unlike Student X's method.

   [6 marks]

   Total for question 4: 12 marks

End of questions