Question

Calculate the number of moles in:

31.9 g of hydrated copper sulphate

Answer 1

Hydrated Copper sulphate is Copper sulphate pentahydrate (CuSO₄.5H₂O)

Given: Weight of Copper sulphate pentahydrate = 31.9 g

Step-1: Calculate the Gram molecular weight of Copper sulphate pentahydrate (CuSO₄.5H₂O)

Gram atomic weight of Hydrogen (H)= 1 g mol^-1

Gram atomic weight of Sulphur (S)= 32 g mol^-1

Gram atomic weight of Oxygen (O)= 16 g mol^-1

Gram atomic weight of Copper (Cu)= 63.5 g mol^-1

As Gram molecular weight is the sum total of the mass of all the atoms.

Hence, Gram molecular weight of Copper sulphate pentahydrate = 10 (gram atomic weight of Hydrogen) + gram atomic weight of Sulphur+ 9 ( gram atomic weight of Oxygen)+ gram atomic weight of Copper

Gram molecular weight of Copper sulphate pentahydrate = 10(1g mol^-1 ) + 32 g mol^-1 + 9 (16g mol^-1) + 63.5g mol^-1

Gram molecular weight of Copper sulphate pentahydrate = 249.5 g mol^-1

Step-2: Calculate the number of moles

$Numberofmoles=\frac{Givenweightofthesubs\tan ce}{Grammolecularweightofthesubs\tan ce}$

$Numberofmoles=\frac{31.9}{249.5}=0.127$ mol

Therefore, the number of moles in 29.4 g of hydrated copper sulphate is 0.127 mol.