Question
Download Solution PDFTemporary hardness in water is due to which one of the following of Calcium and Magnesium?
This question was previously asked in
NDA (Held On: 23 Apr 2017) General Ability Test Previous Year paper
Answer (Detailed Solution Below)
Option 1 : Hydrogen carbonates
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NDA 01/2025: English Subject Test
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Detailed Solution
Download Solution PDFThe correct answer is Hydrogen Carbonates.
Key Points
- Temporary hardness is due to the presence of Calcium hydrogen carbonate Ca(HCO3)2(aq) and Magnesium hydrogen carbonate Mg(HCO3)2(aq).
- The hydrogen carbonates of both Calcium and Magnesium decompose upon heating.
- The original insoluble carbonate is reformed when water is boiled.
- The following is the precipitation reaction -
- Ca(HCO3)2(aq) → CO2(g) + H2O(l) + CaCO3
- Mg(HCO3)2(aq)
→CO2(g) + H2O(l) + MgCO3
- Boiling of water results in the removal of Magnesium and Calcium ions from water, and thus its hardness.
- This is the reason why it is called temporary hardness.
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