Answer: 5 water molecules
Explanation:
Decomposition of hydrated copper sulphate is given by:
[tex]CuSO_4.xH_2O\rightarrow CuSO_4+xH_2O[/tex]
Molar mass of [tex]CuSO_4[/tex] = 159.6 g/mol
According to stoichiometry:
(159.6+18x) g of [tex]CuSO_4.xH_2O[/tex] decomposes to give = 159.6g of [tex]CuSO_4[/tex]
Thus 7.74 g of [tex]CuSO_4.xH_2O[/tex] decomposes to give= [tex]\frac{159.6}{159.6+18x}\times 7.74[/tex] g
But it is given 7.74 g of a sample of hydrated salt was found to contain 4.95 g of anhydrous salt.
Thus we can equate the two equations:
[tex]\frac{159.6}{159.6+18x}\times 7.74=4.95[/tex]
x=5
Thus there are 5 water molecules associated with each [tex]CuSO_4[/tex] formula unit.
