(a) A compound was analyzed and was found to contain the following percentages o
ID: 1002821 • Letter: #
Question
(a) A compound was analyzed and was found to contain the following percentages of the elements by mass: vanadium, 56.01%; oxygen, 43.98%. Determine the empirical formula of the compound.
(b) A compound was analyzed and was found to contain the following percentages of the elements by mass: sodium, 74.19%; oxygen, 25.81%. Determine the empirical formula of the compound.
(c) When iron is heated strongly in an atmosphere of pure chlorine, the product contains , 34.43% Fe and 65.57% Cl on a mass basis. Determine the empirical formula of the compound.
Explanation / Answer
(a) Empirical formula
moles of V = 56.01/50.94 = 1.10 mol
moles of O = 43.98/16 = 2.75 mol
Divide by lowest factor
V = 1.10/1.10 = 1
O = 2.75/1.10 = 2.5
Empirical formula = V2O5
(b) Calculate moles
moles of Na = 74.19/23 = 3.22 mol
moles of O = 25.81/16 = 1.61 mol
Divide by smallest factor
Na = 3.22/1.61 = 2
O = 1.61/1.61 = 1
Empirical formula = Na2O
(c) calculate moles
moles of Fe = 34.43/55.845 = 0.61 mols
moles of Cl = 65.57/35 = 1.87 mols
Divide by smallest factor
Fe = 0.61/0.61 = 1
Cl = 1.87/0.61 = 3
Empirical formula = FeCl3
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