WAEC Chemistry 2011 Theory — Question 30
Question 30 of 31 from the West African Examinations Council (WAEC) Chemistry 2011 Theory paper, with the correct answer and a full explanation.
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8d An industrial raw material has the following composition by mass: iron=28.1%; chlorine=35.7%; water of crystallization=36.2%. Calculate the formula for the material. [H=1.00, O=16.0, Cl=35.5, Fe=56.0]
Model answer
Fe: 28.1/56 = 0.5018. Cl: 35.7/35.5 = 1.006. H2O: 36.2/18 = 2.011. Dividing by the smallest (0.5018): Fe:Cl:H2O = 1 : 2 : 4. Thus, the formula is FeCl2.4H2O.
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