On heating a sample of 25 mg hydrated compound (molecular weight = 250 g/mol) in thermogravimetric analysis, 16 mg of dehydrated compound remains

Q. On heating a sample of 25 mg hydrated compound (molecular weight = 250 g/mol) in thermogravimetric analysis, 16 mg of dehydrated compound remains. The number of water molecules lost per molecule of hydrated compound is                                                                             .

(Molecular weight of water = 18 g/mol)

Solution:

25 mg Compound contains (25-16) g of Water = 9 g of water,

Using,

No. of moles = Given Mass / Molecular Mass

No. of moles = 250 g of the compound will contain 90 g of water; and

250 g of  Water will contain = 90 / 18 moles of Water = 5 moles.