Question

20 g of Ca was burnt in the excess of oxygen and the oxide was dissolved in water to make up a two-litre solution. The normality of alkaline solution is:

Answer 1

The reaction takes place as: 

Ca + 1/2​O₂​→CaO

CaO + H₂​O→Ca(OH)_2​

Atomic weight of Ca = 40

molecular weight of CaO = 56

molecular weight of Ca(OH)₂​ = 74

40 g of Ca produces 74grm of Ca(OH)₂​

1 g of Ca is equivalent to 74/40 ​gm of  Ca(OH)₂​ = 1.85gm.

So 20 g of Ca = 20×1.85 = 37

Or 37/37 = 1 gm equivalent of  Ca(OH)₂​ (Equivalent weight of Ca(OH)₂​ is 37)

Therefore 1 gm is dissolved in 1 litre

Hence in two litre it will be 

So the normality of alkaline solution is 2.0 N