This question is about zinc and compounds of zinc - AQA - GCSE Chemistry - Question 4 - 2022 - Paper 1
Question 4
This question is about zinc and compounds of zinc.
A student produces pure crystals of zinc chloride by reacting zinc oxide with hydrochloric acid.
The equation fo... show full transcript
Worked Solution & Example Answer:This question is about zinc and compounds of zinc - AQA - GCSE Chemistry - Question 4 - 2022 - Paper 1
Step 1
Give one observation that the student could make to show that the zinc oxide is in excess.
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Answer
The student could observe that the zinc oxide solid no longer disappears in the hydrochloric acid solution, indicating that all the acid has reacted.
Step 2
Why is excess zinc oxide used rather than excess hydrochloric acid?
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Answer
Excess zinc oxide can be filtered off more easily after the reaction, ensuring that the hydrochloric acid is completely utilized without leaving unreacted acid in the solution.
Step 3
Name one other compound that the student could add to hydrochloric acid to produce zinc chloride.
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The student could add zinc hydroxide (Zn(OH)₂) or zinc carbonate (ZnCO₃) to hydrochloric acid to produce zinc chloride.
Step 4
Describe how the student should obtain crystals of zinc chloride from a solution of zinc chloride.
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The student should heat the solution until the crystallization point is reached, allowing crystals to form. After crystals start to appear, the solution should be allowed to cool and then left to crystallize fully, or the solution can be gently evaporated to dryness to obtain the crystals.
Step 5
Complete the ionic equation for this reaction.
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The completed ionic equation is: Zn + Cu²⁺ → Zn²⁺ + Cu.
Step 6
Why is zinc described as being oxidised in this reaction?
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Zinc is described as being oxidized because it loses electrons (two electrons) during the reaction, which is the definition of oxidation.
Step 7
Complete Figure 7 to show how zinc, copper and another substance can be used to light a lamp.
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In Figure 7, there should be a diagram showing the zinc and copper electrodes inserted into an electrolyte solution, completing the circuit to light a lamp. The lamp is represented by the symbol ⊗.
