Question

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. $N{a}_{2}C{O}_{3}andMgC{O}_3$

Answer 1

Answer: (C)

calcium carbonate

The carbonate ions from sodium carbonate react with the calcium and magnesium ions in the water to produce insoluble product.

calcium ions + sodium carbonate → calcium carbonate + sodium ions

$C{a}^{+2}+N{a}_{2}C{O}_3\to CaC{O}_3+2N{a}^{+}$

The water is softened because it no longer contains dissolved calcium ions and magnesium ions, hence we can say that it is converted in soft water. It will now form lather easily with soap.