A compound contains equal masses of the elements A, B & C. If the gram atomic masses of A, B & C are 60 g, 20 g & 40 g respectively. Determine the molecular formula of the compound if the molecular mass is 720 g.
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Solution
Let individual mass of A, B & C be x gm
Mass Ratio is A:B:C⇒x:x:x
Mole Ratio is A:B:C⇒x60:x20:x40
On simplification it becomes 2:6:3 ∴EmpiricalFormulabecomesA2B6C3
Hence empirical formula mass = 2×60+6×20+3×40=360g
We know that MolecularFormula=EmpiricalFormula×n
where, n=MolecularMassEmpiricalMass=720360=2 ∴MolecularFormula=(A2B6C3)2
i.e. A4B12C6