Question

4. In a sample of FeO when 12% Fe+2 get replaced by Fe3+. The composition of this wustite sample is

Answer 1

Answer:

12% Fe2+ are being replaced by Fe3+ . So let there be 100 Fe atoms

And we know for 100 Fe there will be 100 O atoms

So, Initially formula is Fe2+100 O2-100

Now 12% i.e, 12 out of 100 Fe2+ are to be replaced

So amount of charge to replaced  12 x +2 = +24

Now 3+ charge will be provided by 1 Fe3+ atom

     +24 charge will be provided by 24/3 = 8 such atoms

So previously after 12 atoms of Fe2+ removed, left Fe2+ = 100-12 = 88

And 8 new Fe atoms join as Fe3+ 

Hence total Fe = 96

total O = 100

100 O require 96 Fe atoms

1 O require 96/100 = 0.96 Fe atoms

So, the composition will be 

Fe0.96O