Question

Permanent hardness of water may be removed by the addition of:

• A. sodium carbonate
• B. alum
• C. potassium permanganate
• D. lime

Answer 1

The correct option is A sodium carbonate

Sodium carbonate, $N{a}_{2}C{O}_3$, 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. The water is softened because it no longer contains dissolved calcium ions and magnesium ions.