In lab we heated copper sulfate pentahydrate (CuSO_4 * 5H_2O) to prove that ther

Question

In lab we heated copper sulfate pentahydrate (CuSO_4 * 5H_2O) to prove that there are 5 moles of water for every mole of CuSO_4. For this problem, I want you to perform the same experiment (on paper only) for Epsom salt, MgSO_4 * xH_2O. A 3.50 g sample of Epsom salt was heated for five minutes and the resulting solid, MgSO_4, had a mass of 1.85 g. From this data determine the number of moles of water lost and the amount of MgSO_4 that remains. Using your data, what is the value of x in the formula for Epsom salt?

Explanation / Answer

mass of Epsom salt MgSo4.XH2O   = 3.5g

mass of MgSo4                               = 1.85g

mass of water = mass of Epsom salt MgSo4.XH2O -mass of MgSo4  

                           = 3.5-1.85 = 1.65g

no of moles of water   = 1.65/18 = 0.0916moles of water

no of moles of MgSo4    = 1.85/120.37   = 0.0154moles

MgSo4 : H2O               = 0.0154 : 0.0916

                                       = 0.0154/0.0154 : 0.0916/0.0154

                                        = 1:6

x = 6

mgSo4 6H2O formular

Actual formula of epsom salt is MgSO4.7H2O

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