A student investigated the reaction between aqueous copper(II) sulfate and two different metals, zinc and iron. Two experiments were carried out.
Experiment 1
Using a measuring cylinder, 25 cm3 of aqueous copper(II) sulfate was poured into a polystyrene cup. The temperature of the solution was measured. The timer was started and the temperature was measured every half a minute for one minute.
At 1 minute, 5 g of zinc powder was added to the cup and the mixture stirred with the thermometer. The temperature of the mixture was measured every half minute for an additional three minutes.
Use the thermometer diagrams in the table to record the temperatures.
time / min | thermometer diagram | temperature / oC |
0.0 |
| |
0.5 |
| |
1.0 |
| |
1.5 |
| |
2.0 |
| |
2.5 |
| |
3.0 |
| |
3.5 |
| |
4.0 |
|
Experiment 2
Experiment 1 was repeated using 5 g of iron powder instead of the zinc powder.
Use the thermometer diagrams in the table to record the temperatures.
time / min | thermometer diagram | temperature / oC |
0.0 |
| |
0.5 |
| |
1.0 |
| |
1.5 |
| |
2.0 |
| |
2.5 |
| |
3.0 |
| |
3.5 |
| |
4.0 |
|
Plot the results of both experiments on the grid below. Draw two smooth line graphs.
Clearly label your graphs.
From your graph, work out the temperature of the reaction mixture in Experiment 1 after 1 minute 15 seconds. Show clearly on the graph how you worked out your answer.
What type of chemical process occurs when zinc and iron react with aqueous copper(II) sulfate?
i) Compare the temperature changes in Experiments 1 and 2.
[1]
ii) Suggest an explanation for the difference in temperature changes.
[1]
Explain how the temperature changes would differ in the experiments if 12.5 cm3 of copper(II) sulfate solution were used.
Predict the effect of using lumps of zinc in Experiment 1. Explain your answer.
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