A hydrated form of copper sulfate (CuSO4⋅xH2O) is heated to drive off all of the water. If there is initially 9.42g of hydrated salt and there is 5.26g of anhydrous CuSO4 after heating, find the number of water molecules associated with each CuSO4 formula unit.

CuSO₄. 7 H₂O

Explanation:

Given dа ta:

Mass of anhydrous CuSO₄ = 5.26 g

Mass of hydrated CuSO₄ = 9.42 g

Number of water molecules associated with CuSO₄ = ?

Solution:

Mass of water = 9.42 g - 5.26 g = 4.16 g

Number of moles of water = mass / molar mass

Number of moles of water = 4.16 g / 18 g/mol

Number of moles of water = 0.23 mol

Number of moles of CuSO₄:

Number of moles = mass / molar mass

Number of moles = 5.26 g / 159.61 g/mol

Number of moles = 0.033 mol

Number of moles of water per mole of CuSO₄:

Number of moles of water / number of moles of CuSO₄

0.23 mol / 0.033 mol

7 moles

CuSO₄. 7 H₂O