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 with state symbols 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
One way to speed up the reaction is to warm the mixture. This increases the kinetic energy of the particles, leading to more frequent and energetic collisions.
Step 3
How could the student know when all the hydrochloric acid has reacted?
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Answer
The student could know that all the hydrochloric acid has reacted when zinc oxide remains, indicating that the reaction is complete and no more acid is available to react.
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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The student could filter the reaction mixture to remove the unreacted zinc oxide, leaving behind the zinc chloride solution.
Step 5
Describe how zinc chloride crystals are produced from zinc chloride solution.
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Answer
Zinc chloride crystals can be obtained by heating the zinc chloride solution to evaporate some of the water. Once the solution is saturated, it can be cooled to allow zinc chloride crystals to form.
Step 6
Suggest the pH at:
- the start before sulfuric acid is added
- the end when sulfuric acid is in excess.
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At the start before sulfuric acid is added, the pH is expected to be in the range of 12-14 since sodium hydroxide is a strong base.
At the end when sulfuric acid is in excess, the pH will be in the range of 0-3 due to the strong acidity of the unreacted sulfuric acid.
Step 7
Complete the symbol equation for the preparation of sodium sulfate.
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Answer
The balanced symbol equation is:
2NaOH+H2SO4→Na2SO4+2H2O
Step 8
What was the hydrogen ion concentration of the hydrochloric acid after water had been added?
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Answer
After water was added, the hydrogen ion concentration would be 0.10 mol/dm³, as the pH increased by 1, which indicates a tenfold decrease in hydrogen ion concentration.
