DRAFT: This module has unpublished changes.

The purpose of this experiment was to the determine the water content of a hydrated salt.  A source of error in this experiment could have been that all of the crystals in the sample were not all dehydrated crystals so this would affect the results overall.  

 

The results of the experiment show that the formula of the hydrated salt is CuSO4·6H2O.

 

The empirical formula of hydrated CuSO4 is CuSO4·5H2O (Pentahydrate).  

 

When heated, the   crystals "melt" at a much lower temperature than the ionic compound Na2SO4 normally does.  This is because although it occurs below the boiling point of water, you are adding more H2O crystals (containing water), therefore it does not take a really high temperature to melt them.  Since there is more water overall, the temperature will already be lower for melting purposes.

 

The hydrated and dehydrated forms of a substance are not two different chemical substances.  They are both the same chemical substance, just changed in their physical form.  When water drops were added to the dehydrated crystals, the substance changed physically back to its hydrated form in turning blue.

 

The molar ratio between CuSO4 and its water content in the hydrated form can be calculated from the number of moles of CuSO4 remaining after heating and from the loss of mass, which can be converted to the number of moles of water.

 

In an analysis of a hydrated CuSO4 sample, there are various sources of error that could cause a lower than actual water to CuSO4 ratio.  Sources of error include, heating the substance too quickly which would result in spattering and loss of some of the sample, partial decomposition of the already anhydrous CuSO4, and the sample not completely losing its water content.

 

Anhydrous and hydrated CuSO4 are related chemically in that they are the same compound with somewhat different physical properties.

 

The most likely reason for not obtaining a ratio of whole numbers for the molar ratio between the CuSO4 and H2O is experimental error.

DRAFT: This module has unpublished changes.