0.499g of cuso4.XH2O when heated to constant weight gave a residue of 0.36g. what is the value of X

1 answer

0.499 g - 0.36 g = 0.139 g = mass H2O expelled.
mols H2O = g/molar mass = 0.139/18 = 0.00772
mols CuSO4 = 0.36/160 = 0.00225
0.00772/0.00225 = 3.5 for X.
I suspect a typo in your post. Check it. X should be 5.0 or very close to that.