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Q45 (NDA-I/2015) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Applied everyday chemistry Answer Verified

Permanent hardness of water is due to the presence of

Result
Your answer: —  Â·  Correct: B
Explanation

Water hardness is classified into temporary and permanent types based on the dissolved mineral salts. Temporary hardness is caused by the presence of dissolved calcium and magnesium bicarbonates (hydrogen carbonates), which can be removed by boiling [1]. In contrast, permanent hardness, also known as non-carbonate hardness, is caused by the presence of sulfates, chlorides, and nitrates of calcium and magnesium. These salts do not precipitate upon boiling and require chemical treatments like the addition of washing soda (sodium carbonate) for removal. Specifically, calcium sulfate and magnesium sulfate are primary contributors to this permanent condition. While sodium and potassium salts may be present in water, they do not contribute to hardness because they do not react with soap to form scum or cause scaling in the same manner as multivalent cations like Ca2+ and Mg2+ [1].

Sources

  1. [1] https://www.sciencedirect.com/topics/engineering/carbonate-hardness
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SIMILAR QUESTIONS

NDA-I · 2011 · Q35 Relevance score: 7.04

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 :

NDA-I · 2017 · Q7 Relevance score: 5.72

Temporary hardness in water is due to which one of the following of Calcium and Magnesium ?

NDA-I · 2013 · Q41 Relevance score: 4.97

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,

NDA-II · 2025 · Q106 Relevance score: 4.56

Which one of the following salts is responsible for temporary hardness of water ?