Determining the Formula of an Unknown Hydrate

Atomic Masses:

Mg- 24.31 g/mol

S- 32.065 g/mol

O- 16 g/mol

(1x 24.31) + (1x 32.065) + (4x 16)

= 24.31 + 32.065 + 64

= 120.275 g/mol

Calculating Moles of Substance

Mole =  Mass/Molar Mass

Mole of anhydrate Epsom salts

Mass= 2.01

Molar Mass= 120.375

Mole= 2.01/120.375

= 0.0167 mol

Calculating Water to Salt Ratio of Epsom Salts

   Moles of H2O

Moles of Epsom salts

=  0.111

   0.0167

= 6.64

= 7

Calculating uncertainties of the moles of Epsom salt

Uncertainty of Mass

 Molar Mass

= 0.002

 120.375

= 0.0002

Calculating Percent Error of Water to Salt ratio of Epsom salt

Expected- Observed

      Expected

= 7- 6.61360925671311 x 100

            7

= 5.519867761241

= 5.51%

Calculating Percent Error of Water to Salt ratio of Copper (II) Sulfate

Expected- Observed

      Expected

= 5- 4.76950823870913 x 100

             5

= 4.609835226

= 4.61%

Data Processing

Table 3. Mass, molar mass, mole of hydrate and water and water to salt ratio

Conclusion

The final equations that was concluded after the experiment and the calculations are

CuSO4 • 5H2O and MgSO4 • 5H2O. There are 5 water molecules per Copper (II) Sulphate and 7 water molecules per Magnesium Sulphate. The compounds are all hydrates which is a substance that contains water. This occurs when crystals form from the evaporation of an aqueous solution of a salt and water molecules become included into the crystal. The hydrates were heated and lost its water of hydration and made it possible to calculate how much water was in the hydrate and the water to salt ratio. The percentage error for the Copper (II) Sulfate was 4.61%. It is a large error but the coefficient was correctly rounded to the accepted value of 5. The percentage error for Epsom salts was 5.51% which is also very large but can also be rounded to the accepted value of 7.

Errors and Limitations