Percentage Composition of an Element in a Compound
Calculate the...
Question
Calculate the percentage composition of iron in ferric oxide, Fe2O3 (atomic mass of Fe=56)
A
70%
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B
56%
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C
87%
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D
35%
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Solution
The correct option is A 70% i) Molecular weight of Fe2O3=(56×2)+(16×3)=160g Molar mass of Fe in 1 mole of Fe2O3=56×2=112g Therefore %age composition of Fe in Fe2O3=molarmassofFeMolecularweightofFe2O3×100=112160×100=70% ii) Molecular weight of Urea( H2NCONH2) =2+14+12+16+2+14=60g Molar mass of N in 1 mole of Urea =2×14=28g Therefore %age composition of N in Urea =molarmassofNMolecularweightofH2NCONH2×100=2860×100=46.6%