Question
Answers

In permanent hardness of water, when washing soda is treated with water, _____is precipitated out
A.Sodium carbonate
B.Magnesium carbonate
C.Calcium carbonate
D.$N{a_2}C{O_3}$ and $MgC{O_3}$

Answer Verified Verified
Hint: Permanent hardness of water is due to presence of soluble chlorides and sulphates of $M{g^{2 + }}$ and $C{a^{2 + }}$. This hardness is removed by washing soda. It is generally difficult to remove the permanent hardness by boiling.

Complete step by step answer:
Washing soda is a chemical compound with the formula $N{a_2}C{O_3}$ known as sodium carbonate, and it is a salt of carbonic acid. It is a natural cleaner and a powerful water softener. It is very basic with a pH of $11$
Now in permanent hardness of water, when washing soda is treated with water, the carbonate ions from sodium carbonate react with calcium and magnesium ions in water and produce an insoluble product.
Hence, the equation is a shown:
$C{a^{2 + }} + N{a_2}C{O_3} \to CaC{O_3} + 2N{a^ + }$
Therefore, calcium carbonate is precipitated out.
Further, the water is softened as it no longer contains dissolved calcium ions and hence it is converted into soft water which may further form lather easily with soap.

Hence, option C is correct.

Note:
Washing soda is a chemical compound that can be used to remove stains from laundry and it is an essential component in most homemade laundry detergents for making powders, liquids or single pod formulas. It is often used in commercial detergent mixtures as well as to treat hard water. It is safe to use and doesn’t