Question

Iron oxide has formula Fe 0.940. What fraction of Fe exists as Fe +3?​

Answer 1

for better reference see the pic attached...

Solution :

Let there are 100 oxide ions and 94 iron ions.

Fe+x:O−2 Total negative charge on 100 oxide ions =-200

=94 :100

It means as per the concept of charge neutrality , 94 iron ions should have total charge of +200

let number of Fe+3=x

∴ Number of Fe+2 =(94-x)

Total positive charge =3x-2(94-x)=200

On solving , x =12

%Fe+3=1294×100 =12.8%