Temporary hard water is formed when rain water containing dissolved carbon(IV) oxide flows over deposits of

  • A CaCO3
  • B Na2CO3
  • C Na2SO4
  • D CaSO4

The correct answer is A. CaCO3

Permanent hardness in water= Mg & Ca Sulphate.

Temporary hardness in water= Mg & Ca Carbonate.

Temporary hardness of water is caused by Magnesium and calcium hydrogencarbonate. It is formed when rainwater containing dissolved CO2 flows over deposit of CaCO3

i.e CaCO3 + CO2 + H2O → Ca(HCO3)2

Previous question Next question