6 (a) A sample of potable water contains impurities - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2021 - Paper 1
Question 6
6 (a) A sample of potable water contains impurities.
Why is this sample of water potable even though it contains impurities?
A. The impurities have no smell
B. Th... show full transcript
Worked Solution & Example Answer:6 (a) A sample of potable water contains impurities - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2021 - Paper 1
Step 1
Why is this sample of water potable even though it contains impurities?
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Answer
C. The impurities are harmless. This indicates that the presence of these specific impurities does not pose a risk to health, allowing the water to be considered safe for consumption.
Step 2
What is sedimentation?
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Answer
C. The impurities in the waste water settle to the bottom of their container. Sedimentation allows solid particles to settle under gravity, resulting in clearer water on the top.
Step 3
State why the waste water is filtered.
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The waste water is filtered to remove suspended solids and impurities, ensuring that the water is made clearer and safer for further treatment processes.
Step 4
State the reason for chlorination.
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Chlorination is done to disinfect the water by killing harmful bacteria and pathogens, making it safe for drinking.
Step 5
Use the information about salt A and salt B in Figure 7 to evaluate this conclusion.
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In the graph shown in Figure 7, it can be observed that adding 100 mg of salt B removes a higher percentage of impurities compared to salt A. This suggests that salt B is more effective as a purifying agent. Thus, the conclusion that adding 100 mg of salt B is the best method for purifying 1000cm³ of waste water is justified. However, further experiments could provide more conclusive evidence.
Step 6
Devise a plan to separate pure water from this mixture, including a test to show that the water obtained is neutral.
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To separate pure water from a mixture contaminated with a dissolved solid, a distillation method can be used. The mixture can be heated until the water evaporates. This vapor can then be cooled and collected as distilled water, which should be neutral. A pH test using pH paper or a pH meter can confirm that the distilled water is neutral (pH 7).
