Question

In permanent hardness of water, when sodium carbonate is treated with water, carbonate is precipitated out.
(a) True
(b) False

Answer 1

We should always remember that the permanent hardness is hardness (mineral content) that can't be removed by boiling. When this is often the case, it's usually caused by the presence of calcium sulphate and/or magnesium sulphates within the water, which don't precipitate out because the temperature increases.

Complete step by step solution:
We know that the most common means for removing water hardness rely on ion-exchange resin or reverse osmosis. Other methods include precipitation methods and sequestration by the addition of chelating agents.
Point to be given preference is that the carbonate ions from sodium carbonate react with the calcium and magnesium ions in the water to produce insoluble products.
$C{a^{2 + }} + N{a_2}C{O_3} \to 2N{a^ + } + CaC{O_3}$
The water is softened because it does not contain dissolved calcium ions and magnesium ions, hence we will say that it's converted into water. It will now form lather easily with soap.
But Permanent hardness of water is due to presence of soluble chlorides and sulphate of magnesium ions and calcium ions.
The permanent hardness of water thanks to calcium ions is removed by sodium carbonate. This method isn't applicable to permanent hardness of water thanks to magnesium salts.
Hence the statement: In permanent hardness of water, when washing soda is treated with water, calcium carbonate is precipitated out is False.

Note:
Hard water is water that has high mineral content in contrast with soft water. Hard water is formed when water percolates through deposits of calcium and magnesium-containing minerals like limestone, chalk and dolomite.