Q. Permanent hardness of water may be removed by addition of: Answer:
Sodium carbonate
Notes: Sodium carbonate (also known as washing soda or soda ash) is a sodium salt of carbonic acid. In domestic use, it is used as a water softener in laundering. sodium ions present in it. competes with the magnesium and calcium ions in hard water and prevents them from bonding with the detergent being used. Sodium carbonate can be used to remove grease, oil and wine stains.