This question is about acids, alkalis and bases - AQA - GCSE Chemistry Combined Science - Question 4 - 2020 - Paper 1
Question 4
This question is about acids, alkalis and bases.
A student reacted zinc oxide powder with hydrochloric acid to produce zinc chloride solution.
Complete the equatio... show full transcript
Worked Solution & Example Answer:This question is about acids, alkalis and bases - AQA - GCSE Chemistry Combined Science - Question 4 - 2020 - Paper 1
Step 1
Complete the equation for the reaction by writing the state symbols.
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Answer
The balanced equation for the reaction is:
ZnO(s)+2HCl(aq)→ZnCl2(aq)+H2O(l)
Step 2
Give one way that the student could speed up the reaction between zinc oxide powder and hydrochloric acid.
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Answer
The student could increase the temperature of the mixture to speed up the reaction.
Step 3
How could the student know when all the hydrochloric acid has reacted?
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Answer
The student could observe that zinc oxide remains in the mixture, indicating that hydrochloric acid has been completely consumed.
Step 4
How could the student obtain zinc chloride solution from the reaction mixture when all the hydrochloric acid has reacted?
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Answer
The student could filter the mixture to remove any unreacted zinc oxide and obtain the clear zinc chloride solution.
Step 5
Describe how zinc chloride crystals are produced from zinc chloride solution.
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Answer
Zinc chloride can be crystallized by heating the solution to evaporate some water, followed by allowing the solution to cool. As it cools, zinc chloride crystals will form.
Step 6
Suggest the pH at the start before sulfuric acid is added.
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Answer
The pH at the start is expected to be around 12-14 as it is a sodium hydroxide solution.
Step 7
Suggest the pH at the end when sulfuric acid is in excess.
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The pH at the end would be in the range of 0-3 as the solution becomes acidic with excess sulfuric acid.
Step 8
Complete the symbol equation for the preparation of sodium sulfate.
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Answer
The balanced equation is:
2NaOH+H2SO4→Na2SO4+2H2O
Step 9
What was the hydrogen ion concentration of the hydrochloric acid after water had been added?
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After adding water, the hydrogen ion concentration would be 0.10 mol/dm³.
