Question

Which of the following process can be remove both temporary and permanent hardness?

• A. Clark's method
• B. addition of washing soda
• C. boiling
• D. all of above

Answer 1

The correct option is B

addition of washing soda

Explanation for correct option:

(b) Addition of washing soda (sodium carbonate) $\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$removes both the temporary and permanent hardness of the water. Bicarbonates, sulfates, and chlorides present in hard water get converted to carbonate which is insoluble in water, and removed by filtration.

Explanation for incorrect option:

(a) Clark's method removes only temporary hardness. In this method added slacked lime (Ca(OH)₂) is added to water either in solid or liquid form. This leads to the conversion of soluble bicarbonates to insoluble carbonates.

(c) Boling can remove only temporary hardness.

Hence B will be the correct option.