A student investigated the temperature change when magnesium was added to copper sulfate solution - AQA - GCSE Chemistry Combined Science - Question 5 - 2020 - Paper 1
Question 5
A student investigated the temperature change when magnesium was added to copper sulfate solution.
This is the method used.
1. Pour 30 cm³ of copper sulfate soluti... show full transcript
Worked Solution & Example Answer:A student investigated the temperature change when magnesium was added to copper sulfate solution - AQA - GCSE Chemistry Combined Science - Question 5 - 2020 - Paper 1
Step 1
What is the dependent variable in this investigation?
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Answer
The dependent variable in this investigation is the temperature change of the mixture.
Step 2
Suggest why the copper sulfate solution was left for four minutes before adding the magnesium.
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Answer
The copper sulfate solution was left for four minutes to allow it to reach a constant temperature before magnesium was added.
Step 3
Complete Figure 4 by:
- drawing a line of best fit through all the points after 7 minutes.
- extending the line back to 4 minutes.
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The line of best fit should show a downward trend through the points after 7 minutes and be extended to connect to the data at 4 minutes.
Step 4
Determine the temperature change for the reaction.
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Answer
At 4 minutes, the temperature was approximately 26.3 °C and at the maximum recorded value shortly after that it was about 17.5 °C. The temperature change is thus calculated as follows:
extTemperaturechange=26.3ext°C−17.5ext°C=8.8ext°C
Step 5
Explain why the temperature of the mixture decreases after 7 minutes.
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The temperature of the mixture decreases after 7 minutes because the reaction has finished or stopped, leading to energy loss to the surroundings or atmosphere; hence, the solution cools back to room temperature.
Step 6
Suggest the identity of metal Q.
Give one reason for your answer.
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Metal Q could be aluminum, zinc, iron, or beryllium because these metals are less reactive than magnesium, resulting in a smaller temperature change.
Step 7
Calculate the mass of copper sulfate in 30.0 cm³ of this solution.
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To find the mass of copper sulfate in 30.0 cm³ of the solution, we first convert the volume into dm³:
30.0extcm3=0.030extdm3
Next, using the molarity:
Moles = 0.100 moles in 0.500 dm³, hence in 0.030 dm³:
