IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry - Numerical problem of Solid State---Chemistry

amanthegame

Composition of a sample of wustite is Fe0.93O1.00.What percentage of iron is present in the form of Fe(III)

shgautham

Oxidation no of O = -2
now if ox no of Fe were = -2
composition would have been FeO

but Fe is in the ratio Fe(0.93)O(1.00)

thus Fe has some atoms in ox no = +2 and some in +3

say if out of 0.93 if Fe is in +3 ox state of an amount "x"
thus it will be in ox state +2 to an amount "0.93 - x"

thus (3)(x) + (2)(0.93 - x) = (2)(1)

solving,
3x + 1.86 - 2x = 2
x = 0.14

ie out of 0.93, Fe is in +3 state in 0.14 atoms

therefore +3 state %age = (0.14 * 100) /0.93
which comes out to be around 15%

regards

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