Water that is safe to drink contains dissolved substances - AQA - GCSE Chemistry Combined Science - Question 1 - 2019 - Paper 2
Question 1
Water that is safe to drink contains dissolved substances.
1. What do we call water that is safe to drink?
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Worked Solution & Example Answer:Water that is safe to drink contains dissolved substances - AQA - GCSE Chemistry Combined Science - Question 1 - 2019 - Paper 2
Step 1
What do we call water that is safe to drink?
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Answer
Potable
Step 2
Describe a test for pure water.
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Answer
Test: Boil (water)
Result: Boils at 100°C
Step 3
Describe a method to determine the mass of dissolved solids in a 100 cm³ sample of river water.
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Answer
Weigh an empty container.
Measure a 100 cm³ sample of river water into the container.
Evaporate the water by heating until dry.
Weigh the container with the remaining solids to determine the mass of dissolved solids.
Step 4
A sample of river water contains 125 mg per dm³ of dissolved solids. Calculate the mass of dissolved solids in grams in 250 cm³ of this sample of river water.
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Answer
Given that the concentration is 125 mg per dm³, we convert this to grams: rac{125 ext{ mg}}{1000} = 0.125 ext{ g}.
For 250 cm³, we use the conversion: 0.125 ext{ g} imes rac{250}{1000} = 0.03125 ext{ g}, rounded to 2 significant figures gives 0.031 g.
Step 5
Calculate the percentage (%) of the maximum allowed mass of sulfate ions in the sample of drinking water.
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Answer
To find the percentage of sulfate ions: rac{44 ext{ mg}}{500 ext{ mg}} imes 100 = 8.8 \%.
