Question #64fe5

1 Answer

Magnesium sulfate in the hydrated form has a formula of #MgSO_4#x7#H_2O# and can be called magnesium sulfate heptahydrate.

The purpose of heating the sample twice is to make sure that all of the water has been removed to produce the anhydrous form (which is completely dried) of magnesium sulfate that has no remaining water.

The change in mass from the hydrated form (wet) and the anhydrous form (dry) will allow for a determination of the mass of water in the initial sample. This will allow a calculation of the moles of water.

The mass of the dry form can be converted to moles of magnesium sulfate.

The final step is to compare the mole ratios of #MgSO_4# and #H_2O# which should work out to be 1:7.

Making sure to dry the sample twice reduces the most important source of error in this experiment which would be not having a sample which is fully dried. This would lead to an under-reporting of the water content and an over-reporting of the #MgSO_4# content of the hydrate.