Determination of the amount of water present in copper sulfate hydrate

Example of calculation ( data from first measurement):

Mass of hydrated salt = (Mass of the test tube +  hydrated

        salt) - Mass of the test tube         

= 19.6 – 19.0

= 0.6 g

Mass of anhydrous salt = (Mass of the test tube + anhydrated salt) - Mass of the test tube

        = 19.4 – 19.0 = 0.4 g

Mass of water lost         = Mass of hydrated salt - Mass of

anhydrous salt        

= 0.6  - 0.4

= 0.2 g

Mole of CuSO4                = mass of CuSO4 / molar mass of CuSO4

= 0.4 g / 159.61 g/mol                                 = 0.0025 mol

Mole of H2O                = mass of H2O / molar mass of H2O

= 0.2 g / 18.01 g/mol

= 0.0111 mol

Mole ratio                 = mole CuSO4: mole H2O

                                = 0.0025 : 0.0111

                                = 1 : 4

Therefor the value of x is 4 and the formula of copper sulfate hydrate is CuSO4. 4H2O

Concluison:

Copper to sulfate usually found on hydrate form, because it absorbs water easliy. The copper sulfate and water absorbed forming a weak bond, so the water could be released easily when this compound is heated. The amount of water present in this compound could be determine from the mass lost after the compound is heated. From this experiment the mole ratio between copper sulfate and water is 1 : 4. Therefor the sample of Copper Sulfate could be written as CuSO4. 4H2O or Copper Sulfate tetrahydrate.

The Copper II sulfate hydrate mostly exist in pentahydrate form or the mole ratio between Copper Sulfate and Water is 1 : 5. This true value of mole of Water is bigger than the value obtained from the experiment.  It can be happend because the uncertainty that may occurs such as the water that evaporte was reabsorb by the sample. It makes the sample of Copper Sulfate anhydrous still contain a small amount of Water and it affect to the experimental data.  

"Copper(II) Sulfate." Wikipedia, the Free Encyclopedia. 8 Sept. 2011. Web. 12 Sept. 2011. <http://en.wikipedia.org/wiki/Copper(II)_sulfate>.

Evaluation:

The method in this experiment can be used to determine the amount of water present in a sample that forming weak bond with a number of water molecules. The data obtain from the experiment could be different because the sample is highly hygroscopisch.  The determination process that use this method should be repeated to get more accurate data. The data from the third measurement is far different rather then the data obtained from the first and second one it could be happend because of the uncertainty that mention above. The heating process is could be not constant because we use the bunsen burner that its temperature can not be control.