Types of chemical reactionIB MYP Chemistry: Subtopic test

1. 1
   A teacher in Ghana heats green copper(II) carbonate powder, CuCO₃, in a test tube. The powder turns black as copper(II) oxide forms, and a gas that turns limewater milky is given off.

   (a)

   What type of reaction takes place when copper(II) carbonate is heated?

   [1 mark]

   • AThermal decomposition
   • BNeutralisation
   • CPrecipitation
   • DSynthesis

   (b)

   Which is the correct balanced symbol equation for the reaction?

   [1 mark]

   • ACuCO₃(s) → Cu(s) + CO₃(g)
   • BCuCO₃(s) → CuO₂(s) + CO(g)
   • C2CuCO₃(s) → CuO(s) + CO₂(g)
   • DCuCO₃(s) → CuO(s) + CO₂(g)

   (c)

   Explain what is meant by thermal decomposition, and describe how the mass of the solid in the test tube changes.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A metalworker in Peru places a clean iron nail in blue copper(II) sulfate solution. After some minutes the nail is coated with a brown solid and the blue solution fades to pale green as iron(II) sulfate forms.

   (a)

   What type of reaction takes place between the iron nail and the copper(II) sulfate solution?

   [1 mark]

   • AThermal decomposition
   • BPrecipitation
   • CSingle displacement
   • DNeutralisation

   (b)

   Why does the iron displace the copper?

   [1 mark]

   • ACopper is more reactive than iron
   • BIron is more reactive than copper
   • CIron is a solid and copper sulfate is a solution
   • DThe solution is blue

   (c)

   Write the balanced symbol equation, with state symbols, for the reaction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student tests three metals, magnesium, zinc and copper. She places a strip of each metal into separate solutions of the sulfates of the other two metals and records what happens. Magnesium in zinc sulfate solution: a grey coating forms. Magnesium in copper(II) sulfate solution: a brown coating forms and the blue colour fades. Zinc in copper(II) sulfate solution: a brown coating forms and the blue colour fades. Zinc in magnesium sulfate solution: no change. Copper in zinc sulfate solution: no change. Copper in magnesium sulfate solution: no change. Each test used the same volume of solution at room temperature.

   (a)

   State a testable hypothesis for the student's investigation, give a scientific reason, and identify the independent variable.

   [3 marks]

   (b)

   Use the results to put the three metals in order of reactivity, and evaluate the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A metal-plating factory in Vietnam produces waste water that contains hydrochloric acid and dissolved copper(II) sulfate. Before the water can be released, the factory adds sodium hydroxide solution. This neutralises the acid and also removes copper ions from the water as a blue solid, which is filtered off as sludge.

   (a)

   Identify the two types of reaction taking place when sodium hydroxide is added, and write the balanced symbol equation, with state symbols, for each reaction.

   [6 marks]

   (b)

   Discuss whether factories should be legally required to treat waste water in this way before releasing it.

   [6 marks]

   Total for question 4: 12 marks

End of questions