Which of the following statements regarding the property of hard water is/are correct? 1. Temporary hardness of water is due to the presence of soluble magnesium and calcium hydrogen carbonate. 2. Temporary hardness of water can be removed by boiling. 3.

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Q: 41 (NDA-I/2013)

Which of the following statements regarding the property of hard water is/are correct?
1. Temporary hardness of water is due to the presence of soluble magnesium and calcium hydrogen carbonate.
2. Temporary hardness of water can be removed by boiling.
3. Calgon's method is applied to remove temporary hardness of water.
4. Permanent hardness of water is removed by Clark's method.
Select the correct answer vising the code given below,

question_subject: 

Science

question_exam: 

NDA-I

stats: 

0,45,58,45,31,19,8

keywords: 

{'hard water': [0, 0, 0, 2], 'temporary hardness': [0, 0, 0, 3], 'permanent hardness': [0, 0, 0, 3], 'calcium hydrogen carbonate': [0, 0, 0, 1], 'water': [65, 15, 80, 129], 'property': [15, 0, 8, 22], 'soluble magnesium': [0, 0, 0, 1]}

The correct answer is option 1, which states that both statement 1 and statement 2 are correct.

Statement 1 is correct because temporary hardness of water is indeed caused by the presence of soluble magnesium and calcium hydrogen carbonate. Temporary hardness occurs when these compounds dissolve in water, resulting in the formation of calcium and magnesium ions.

Statement 2 is also correct because boiling can remove temporary hardness. When water is boiled, the soluble magnesium and calcium hydrogen carbonate decompose, forming insoluble calcium carbonate and magnesium hydroxide. These precipitates can then be removed through filtration or settling.

Statements 3 and 4 are incorrect. Calgon`s method, mentioned in statement 3, is not used to remove temporary hardness, but rather to prevent the adverse effects of hard water by binding to calcium and magnesium ions. Clark`s method, mentioned in statement 4, is not used to remove permanent hardness, but rather to determine the permanent hardness of water through a titration method.

It is important to note that permanent hardness of water can only be removed through ion exchange or chemical processes. Therefore, statement 4 is incorrect as well.

In conclusion, option 1 is the correct answer, as both statement 1 and statement 2 correctly describe the property of hard water.

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