A student investigated how a change in concentration affects the rate of the reaction between zinc powder and sulfuric acid - AQA - GCSE Chemistry - Question 9 - 2021 - Paper 2
Question 9
A student investigated how a change in concentration affects the rate of the reaction between zinc powder and sulfuric acid.
The equation for the reaction is:
Zn(s)... show full transcript
Worked Solution & Example Answer:A student investigated how a change in concentration affects the rate of the reaction between zinc powder and sulfuric acid - AQA - GCSE Chemistry - Question 9 - 2021 - Paper 2
Step 1
The student made an error in setting up the apparatus in Figure 8. What error did the student make?
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Answer
The delivery tube is in sulfuric acid, which can cause backflow and create inaccuracies in measurement.
Step 2
Explain why the lines of best fit on Figure 9 become horizontal.
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Answer
The horizontal lines indicate that the reaction has stopped because one of the reactants has been completely consumed, resulting in no further gas production.
Step 3
How does Figure 9 show that zinc powder reacts more slowly with 0.05 mol/dm³ sulfuric acid than with 0.10 mol/dm³ sulfuric acid?
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Answer
The graph shows that the reaction with 0.05 mol/dm³ sulfuric acid increases at a slower rate, as indicated by a less steep gradient compared to the reaction with 0.10 mol/dm³ sulfuric acid.
Step 4
Determine the rate of the reaction for 0.05 mol/dm³ sulfuric acid at 80 seconds. Show your working on Figure 9. Give your answer to 2 significant figures.
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Answer
At 80 seconds, using the tangent to find the change in volume of gas:
Find the volume at 80 seconds (let’s say it’s X cm³).
Determine the change in volume over a small time interval (for example, from 70 to 80 seconds, say it’s Y cm³).
Rate = ( \frac{Y \text{ cm}^3}{10 \text{ s}} ).
Provide the final answer rounded to 2 significant figures.
Step 5
What is the most likely formula of the metal ions added? Tick (✓) one box.
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Answer
The most likely formula of the metal ions added is Cu²⁺.
