Given
Hydrated salt
Na2SO4.nH2O Loss of weight on heating = 55.9 %
We have to find the value of 'n'.
Now, gram molecular mass of anhydrous salt,
Na2SO4 = 2 × 23 + 32 + 4 × 16
= 46 + 32 + 64
= 142 g
Let mass of hydrated salt be x g.
The loss of weight on heating is due to loss of water molecules, thus.
Mass of hydrated salt -
× mass of hydrated salt = Mass of anhydrous salt
x -
= 142
= 142
x = 322 g
Thus, mass of
H2O in
Na2SO4.nH2O = Mass of
Na2SO4.nH2O - Gram molecular Mass of
Na2SO4 = 322 - 142
= 180 g
Now, molecular mass of
H2O = 2 × 1 + 16
= 18 g
Now, number of moles is given as :
Number of moles =
Thus, moles of water , n =
= 10
Therefore, the formula of
Na2SO4.nH2O is
Na2SO4.10H2O Hence, option 'D' is correct.