General Knowledge - General Science - Discussion


Permanent hardness of water may be removed by the addition of

[A]. sodium carbonate
[B]. alum
[C]. potassium permanganate
[D]. lime

Answer: Option A


No answer description available for this question.

Abinaya said: (Aug 21, 2011)  
Permanent hardness is due to magnesium or calcium chloride. Therefore by the addition of sodium carbonate it is removed in the form of sodium chloride.

Mayuresh Sunny said: (Sep 24, 2012)  
Thats is why sodium carbonate is also used for detergents.

Abi said: (Mar 19, 2013)  
What is meant by permanent hardness of water?

Suman Moktan said: (Jul 7, 2013)  
The hardness of water can be either temporary or permanent.

Temporary hardness can be removed simply by boiling the water.

Permanent hardness cannot be removed by boiling but can often be removed by chemical treatment.

Temporary hardness is caused by calcium and/or magnesium hydrogencarbonate. These are formed as carbonated rain water passes over rocks containing carbonate ions, for example,

H2O(l) + CO2(g) + CaCO3(s) Ca(HCO3)2(aq).

H2O(l) + CO2(g) + MgCO3(s) Mg(HCO3)2(aq).

Permanent hardness is caused by calcium and/or magnesium sulphate. These are formed as water passes over rocks containing sulphate ions, for example,

aq. + CaSO4(s)Ca2+(aq) + SO42-(aq).

aq. + MgSO4(s)Mg2+(aq) + SO42-(aq).

Abdul Saboor said: (Jan 8, 2016)  
What is reference standard?

Why we use caco3 for finding the strength of degree of hardness?

Subrajit said: (Apr 20, 2016)  
What is the chemical reaction?

Jasna said: (Oct 11, 2016)  
Washing soda is called sodium carbonate.

Shazia Khan said: (May 5, 2017)  
Yes, in hard water magnesium bicarbonate, chloride-bicarbonate.

So they can be removed by Na2co3.

Mehdi said: (Oct 28, 2017)  
Would salt in water is temporary or not?

Pooja said: (Oct 11, 2019)  
Sodium carbonate is used to remove both permanent and temporary hardness of the water.

Permanent hardness is due to the presence of sulfate, chloride, nitrate of magnesium and calcium.

Temporary hardness is due to the bicarbonate of calcium and magnesium.

Harry said: (Dec 17, 2020)  
Sodium carbonate, Na2CO3, is also known as washing soda. It can remove temporary and permanent hardness from water. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.

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