Question

Cu(II) sulfate exists as a hydrate. It has many practical uses including use as a fungicide and pesticide. When mixed with chromium and arsenic it forms the wood preservative called CCA. CCA was used in pressure treated wood to protect wood from rotting due to insects and microbial agents. Because CCA-treated wood contains toxic heavy metals, its use has been discontinued for home use and children’s play sets.

A chemist is given a sample of the CuSO₄ hydrate and asked to determine the empirical formula of it. The original sample weighed 42.75 g. After heating to remove the waters of hydration, the sample weighed 27.38 g. Determine the formula for this hydrate.

Please show all work!

Answer 1

sampla mass = 42.75 g

after heating mass = 27.38 g

mass of water driven off = 42.75 -27.38

                                       = 15.37 g

moles of water = 15.37 / molar mass of water

                        = 15.37 / 18

                        = 0.854

moles of Cu(II) sulfate = 27.38 / 159.6

                                    = 0.172

by divide smallest whole number

CuSO4 = 0.172 / 0.172 = 1

H2O = 0.854 / 0.172 = 4.965 (nearly 5)

so

formula of hydrate : CuSO4 .5H2O