Question

3.22g of hydrated sodium sulphate, Na2SO4 X H2O were hearted to a constant mass of
1.42 g. Determine the value of x in the formula ( Na=23.0, s = 32.0, O = 16, H = 1)

Answer 1

3.22 g = Na2SO4.xH2O before heating
-1.42 g = Na2SO4.xH2O after heating
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1.80 g = mass H2O expelled.
Convert to mols.
mols Na2SO4 = g/molar mass = 1.42/142 = 0.01
mols H2O = 1.80/18 = 0.1
Now find the ratio of Na2SO4 to H2O. The easy way to do this is to divide both number of the smaller number; i.e.,
mols Na2SO4 = 0.01/0.01 = 1
mols H2O = 0.1/0.01 = 10.
Formula is Na2SO4.10H2O

Answer 2

have no idea