Single correct option
Consider the following statements:
1. Permanent hardness of water cannot be removed by boiling.
2. Washing soda (sodium carbonate) can remove both temporary and permanent hardness.
Which of the statements given above is/are correct?
1. Permanent hardness of water cannot be removed by boiling.
2. Washing soda (sodium carbonate) can remove both temporary and permanent hardness.
Which of the statements given above is/are correct?
- A. 1 only
- B. 2 only
- C. Both 1 and 2
- D. Neither 1 nor 2
Show answer and solution
Answer: (C) Both 1 and 2
Temporary hardness is due to bicarbonates of calcium and magnesium, which precipitate as carbonates on boiling. Permanent hardness comes from chlorides and sulphates of these metals, which are unaffected by boiling, so statement 1 is correct. Washing soda precipitates calcium and magnesium as insoluble carbonates, removing both types, so statement 2 is also correct.
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