Question

Which of the following compounds is used for removing permanent hardness of water?

Options

• Bleaching powder

• Washing soda

• Baking soda

• Caustic soda

Answer 1

Washing soda

Explanation:

Washing soda (sodium carbonate) reacts with the soluble calcium and magnesium sulphates and chlorides that cause permanent hardness. This chemical reaction converts them into insoluble carbonates, which precipitate out of the water. Once these minerals are removed as solids, the water becomes soft and can easily form a lather with soap.