5 water molecules are there for each unit of copper(ii) sulfate.
Copper (ii) sulfate is CuSO4. x H2O
Molecular weight = 65.54 + 32 + 64 + 18x
= 159.54 + 18x
Water of crystallization are water molecules that are present inside crystal.
As it is given that 25.5% copper of mass is there, then we have
63.54/(159.54 + 18x) = 25.5/100
6354 = 4068.27 + 459x
x = 4.979
≈ 5
Therefore the water molecules are 5 for each unit of copper (ii) sulfate.
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