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 complete equation 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 effective collisions.
Step 3
How could the student know when all the hydrochloric acid has reacted?
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Answer
The student could tell that all the hydrochloric acid has reacted when zinc oxide remains undissolved in the mixture, indicating that the acid has been fully 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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The student could filter the mixture to remove any undissolved 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 solution to evaporate water, allowing the solution to cool and form crystals as it becomes supersaturated.
Step 6
Suggest the pH at the start before sulfuric acid is added.
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The pH at the start before sulfuric acid is added is approximately 12-14, as sodium hydroxide solution is basic.
Step 7
Suggest the pH at the end when sulfuric acid is in excess.
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The pH at the end when sulfuric acid is in excess is in the range of 0-3, indicating a strongly acidic solution.
Step 8
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 9
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 of the hydrochloric acid decreased to 0.10 mol/dm³.
