Question

In anon stochiometric sample of ferrous oxide with Nacl str. The ratio of Fe3+ to Fe2+ was found to be 0.15 calculate fraction of octahedral sites occupied by vacanies

Answer 1

This is a charge balancing question.  

Fe exists in two forms mainly Ferrous (Fe2+) and Ferric (Fe3+).

Let there are 100 oxygen atoms and x number of Fe3+ atoms and 96-x number of Fe2+ atoms.