The ortho and para hydrogen differ in respect of which of the following ?

• In the molecular weight

• In the nature of spin of protons

• In the nature of spin of electrons

• In the number of protons

Permanent hardness can be removed by adding

• Cl₂

• Na₂CO₃

• Ca(OCl)Cl

• K₂CO₃

Water gas is :

• CO + N₂

• CO + CO₂ + CH₄

• CO₂ + N₂

• CO + H₂

Alums are used for

• tanning of leather

• coagulation of blood

• purification of water

• all of the above

305.

The method used to remove temporary hardness of water is :

• Clark's method

• Ion-exchange method

• Synthetic resins method

• Calgon's method