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A student investigated the temperature change when zinc reacts with copper sulfate solution - AQA - GCSE Chemistry - Question 2 - 2015 - Paper 2
Question 2
A student investigated the temperature change when zinc reacts with copper sulfate solution. The student used a different concentration of copper sulfate solution f... show full transcript
Worked Solution & Example Answer:A student investigated the temperature change when zinc reacts with copper sulfate solution - AQA - GCSE Chemistry - Question 2 - 2015 - Paper 2
Step 1
Step 2
Suggest one improvement the student could make to the apparatus in Figure 3. Give a reason why this improves the investigation.
Answer
Improvement: The student could use a polystyrene cup to insulate the reaction.
Reason: This would reduce heat loss to the environment, leading to more accurate temperature measurements.
Step 3
Describe and explain the trends shown in the student's results.
Answer
The student's results show that as the concentration of copper sulfate increases, the increase in temperature also rises.
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Temperature Change: For example, with 0.1 moles per dm³, the increase in temperature is 5°C, while at 0.5 moles per dm³, it reaches 25°C. This indicates a direct correlation between the concentration of the reactant and the thermal energy produced.
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Anomalous Result: However, there is an anomalous result at experiment 3 where the temperature increase recorded is lower than expected despite the increase in concentration.
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Plateau Effect: Beyond a certain concentration, particularly from experiment 7 onwards, the temperature increase levels off at 35°C even with increased concentration, suggesting that once copper sulfate is in excess, further reaction does not yield additional heat.
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Exothermic Reaction: The overall reaction is exothermic, meaning it releases heat as zinc reacts with copper sulfate, supporting the observed temperature rises up to a point before plateauing.