Each copper(II) sulfate unit is associated with five water molecules in crystalline copper(II) sulfate pentahydrate (CuSO
4·5 H
2O). When this compound is heated in air above 100°C, it loses the water molecules and also its blue color.
CuSO4·5 H2O
CuSO4 + 5 H2O
If
7.90 g of CuSO
4 are left after heating
12.35 g of the blue compound, calculate the number of moles of H
2O originally present in the compound.

Enter a number with the correct number of significant figures.
1 moles