Question

Which one of the following processes will produce hard water ?

• A. Saturation of water with $CaCO _{3}$
• B. Saturation of water with $MgCO _{3}$
• C. Saturation of water with $CaSO _{4}$
• D. Addition of $Na _{2} SO _{4}$ to water

Answer 1

Answer: (C)

Saturation of water with $CaSO _{4}$

Answer 2

Alkaline earth metal salts are causing hardness : Temporary hardness caused by soluble Ca and $Mg$ hydrogen carbonates. calcium and magnesium soluble sulphates and chlorides cause permanent hardness