A hydrate of copper (II) sulfate with formula CuSO4.xH2O has a molar mass of 250.0 g/mol. 2.545 g of hydrate is heated and 63.85% of the residue is found after heating.

Question

a) Determine the value of x in the formula of the compound
b) What is the molecular formula of the hydrate?

Answer 1

mass hydrate before heat = 2.545 g
mass hydrate after heat = 2.545 x 0.6385 = 1.625 g = mass CuSO4
mass H2O = 2.545-1.625 = 0.9200 g
mols H2O = 0.9200/18 = 0.0511
mols CuSO4 = 1.625/159.6 = 0.01

Convert to integers and round to whole numbers for find answer to b. That will give you answer to a.
You can work this another way using the 250 g/mol in the problem and I did it another way.

Answer 2

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Answer 3

CuSo4.xHO