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 completed 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 effective method to speed up the reaction is to warm or heat the mixture, which increases the kinetic energy of the particles involved, leading to more frequent and successful collisions.
Step 3
How could the student know when all the hydrochloric acid has reacted?
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The student can determine when all the hydrochloric acid has reacted by observing that any excess zinc oxide remains undissolved in the solution.
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 can filter the reaction mixture to remove the excess zinc oxide, allowing the clear zinc chloride solution to pass through.
Step 5
Describe how zinc chloride crystals are produced from zinc chloride solution.
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Answer
Zinc chloride crystals can be produced by heating the solution to evaporate some of the water. As the solution becomes more concentrated, zinc chloride will start to crystallize as it reaches its saturation point. The crystals can then be collected once the solution cools.
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 likely to be around 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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When sulfuric acid is in excess, the pH would typically be 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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After adding water to increase the pH by 1, the hydrogen ion concentration of the hydrochloric acid would decrease to 0.1 mol/dm³.
