Question

When a student boiled the given sample of water containing temporary hardness, he observed that it now gave good amount of lather because by boiling: (a) the bicarbonate of sodium decomposes (b) the bicarbonate of magnesium decomposes (c) the bicarbonate of zinc decomposes (d) the bicarbonate of aluminium decomposes

Answer 1

Answer:

(B) The bicarbonate of magnesium decomposes

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Explanation:

Answer 2

When a student boiled the given sample of water containing temporary hardness, he observed that it now gave good amount of lather because by boiling (b) the bicarbonate of magnesium decomposes.

Explanation:

Water : Its molecular formula is H₂O.

Types of water :

• Hard water
• Soft water

Hard water

1. It does not produce lather with soap readily .
2. Hard water contains Calcium and magnesium salts in it mainly bicarbonates ,chlorides ,sulphates .
3. Example : water of sea , river etc

Soft water

1. It can produce lather with soap readily .
2. It doesn't have such ions .
3. Example : Distilled water , rain water etc
4. It doesn't have such ions .

Hardness of water : It can be temporary or permanent .

Permanent hardness

• It is due presence of soluble chlorides ,sulphates of calcium and Magnesium .
• It can't be removed by boiling or heating .Special methods have to be employed for it .

Temporary hardness

• It is due to Bicarbonates of calcium and Magnesium and can be easily removed by boiling .
• On boiling : Mg(HCO₃)₂------------->  MgCO₃ + CO₂ + H₂O
• This magnesium carbonate precipitates and stays behind and id filtered.