M BaCl2= 137+ 71= 208
cristalohidrat BaCl2 . xH2O⇒M cristalohidrat= 208+ 18x
100g cristalohidrat.......................14,7g H2O
(208+18x) g cristalohidrat............(18x)g H2O
1800x= 14,7(208+18x)
1800x=3057,6+264,6x
1535,4x=3057,6
x=2
formula cristalohidrat= BaCl2 . 2H2O