Chemistry
Temporary hardness of water can be removed by:
- Adding sodium chloride
- Boiling
- Adding calcium carbonate
- Leaving it for a few hours.
Water
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Answer
Boiling
Reason — By boiling carbon dioxide is driven off and the soluble hydrogen carbonates are converted into insoluble carbonates and could be removed by filtration or decantation.
Calcium carbonate and magnesium carbonate are precipitated leaving the water soft.
Ca(HCO3)2 CaCO3 ↓ + H2O + CO2 ↑
Mg(HCO3)2 MgCO3 ↓ + H2O + CO2 ↑
Sodium chloride does not remove hardness. Calcium carbonate is insoluble and does not remove hardness. Temporary hardness does not disappear on standing; it requires heating.
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Related Questions
If a salt on heating does not gives water vapour, then that salt is:
- Hygroscopic
- Deliquescent
- Hydrated
- Anhydrous
The salt which is the cause of hardness in water:
- Sodium sulphate
- Magnesium bicarbonate
- Sodium chloride
- Calcium nitrate
The salt which does not contain any water of crystallisation is :
P — Blue vitriol
Q — Gypsum
R — Baking soda
- Only P
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- Both Q and R
Sodium chloride (common salt) besides being used in kitchen can also be used as the raw material for making:
P — Slaked lime
Q — Washing soda
R — Baking soda
- Only P
- Only Q
- Only R
- Both Q and R