copper sulfate pentahydrate, CuSo4 * 5 H2O. a 3.0000 g sample of the bright blue substance is strongly heated until a constant weight is obtained. the pale gray-white rsidue is found to weigh 1.6762 g. what is the actual formula for the copper sulfate hydrate.
Given the pale gray-white residue is CuSO4 and the mass of CuSO4 obtained is 1.6762 g
Molar mass of CuSO4 is = 63.5 + 32 + (4x16) = 159.5 g/mol
Number of moles of CuSO4 is n = mass/molar mass
= 1.6762 g / 159.5 (g/mol)
= 0.01 mol
Let the formula for the copper sulfate hydrate is CuSO4 .aH2O
Molar mass of CuSO4 .aH2O is = Molar mass of CuSO4 + (a x molar mass of H2O)
= 159.5 + (a x 18 )
= 159.5+18a
Given mass of sample is 3.0000 g
Number of moles of CuSO4 .aH2O is , n' = mass/molar mass
= 3.0000 g / (159.5+18a) (g/mol)
CuSO4 .aH2O CuSO4 + aH2O
1 mole of CuSO4 .aH2O produces 1 mole of CuSO4
0.01 mole of CuSO4 .aH2O produces 0.01 mole of CuSO4
So number of moles of CuSO4 .aH2O = 0.01
3.0000 / (159.5+18a) = 0.01
(159.5+18a) = 300
18 a = 140.5
a = 7.8
Therefore the actual formula for the copper sulfate hydrate is CuSO4 7.8 H2O
Get Answers For Free
Most questions answered within 1 hours.