Which of the statements given below is/ are correct ? Permanent hardness of water is due to the presence of soluble : 1. chloride of calcium. 2. bicarbonate of calcium. 3. sulphate of magnesium. 4. bicarbonate of magnesium. Select the correct answer using

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Q: 35 (NDA-I/2011)

Which of the statements given below is/ are correct ? Permanent hardness of water is due to the presence of soluble :
1. chloride of calcium.
2. bicarbonate of calcium.
3. sulphate of magnesium.
4. bicarbonate of magnesium.
Select the correct answer using the code given below :

question_subject: 

Science

question_exam: 

NDA-I

stats: 

0,24,22,3,24,15,4

keywords: 

{'chloride': [0, 0, 0, 1], 'permanent hardness': [0, 0, 0, 3], 'magnesium': [1, 0, 2, 3], 'sulphate': [0, 0, 0, 3], 'calcium': [2, 0, 0, 4], 'water': [65, 15, 80, 129], 'bicarbonate': [0, 0, 0, 1]}

The correct answer is option 2: 1 and 3 only.

To understand why, let`s break down the options:

1. Chloride of calcium: This is incorrect. Chloride salts do not contribute to permanent hardness. They only cause temporary hardness.

2. Bicarbonate of calcium: This is correct. Bicarbonate salts, such as calcium bicarbonate, contribute to permanent hardness. When heated, they break down into insoluble calcium carbonate, causing the formation of scale in pipes and appliances.

3. Sulphate of magnesium: This is correct. Sulphate salts, such as magnesium sulphate, also contribute to permanent hardness. They form precipitates when heated, leading to the formation of scale.

4. Bicarbonate of magnesium: This is incorrect. While bicarbonate salts do contribute to permanent hardness, magnesium bicarbonate is not soluble and does not cause permanent hardness.

Thus, the correct answer is option 2 as it includes the correct statements: 1 (bicarbonate of calcium) and 3 (sulphate of magnesium).

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