9. (a) What is hard water?
Would you expect the water supply in a limestone district to be hard? Give a reason for your answer - Leaving Cert Chemistry - Question 9 - 2014
Question 9
9. (a) What is hard water?
Would you expect the water supply in a limestone district to be hard? Give a reason for your answer.
Distinguish between temporary hardnes... show full transcript
Worked Solution & Example Answer:9. (a) What is hard water?
Would you expect the water supply in a limestone district to be hard? Give a reason for your answer - Leaving Cert Chemistry - Question 9 - 2014
Step 1
What is hard water?
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Answer
Hard water is defined as water that does not easily form lather with soap and may produce a scum instead. This phenomenon occurs due to the presence of minerals, primarily calcium (Ca²⁺) and magnesium ions (Mg²⁺), that create insoluble salts when in contact with soap.
Step 2
Would you expect the water supply in a limestone district to be hard? Give a reason for your answer.
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Yes, the water supply in a limestone district is likely to be hard. This is because limestone, which is primarily composed of calcium carbonate (CaCO₃), dissolves in rainwater, leading to an increase in calcium ions in the water. As these minerals contribute to water hardness, it is expected that the water from such areas would exhibit hard water characteristics.
Step 3
Distinguish between temporary hardness and permanent hardness of water.
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Temporary hardness is caused by the presence of dissolved bicarbonate minerals, which can be removed by boiling since they precipitate as carbonate salts. In contrast, permanent hardness is due to the presence of sulfate and chloride salts of calcium and magnesium, which remain dissolved in water and cannot be removed simply by boiling.
Step 4
State one advantage of a hard water supply.
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One advantage of hard water supply is that it is beneficial for dental and bone health due to the presence of calcium ions.
Step 5
State one disadvantage of a hard water supply.
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One disadvantage of hard water supply is that it can lead to the buildup of scale in pipes and appliances, reducing their efficiency and lifespan.
Step 6
1.
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solid
Step 7
2.
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sedimentation
Step 8
3.
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micro-organisms
Step 9
4.
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nitrates
Step 10
5.
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eutrophication
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