Question

1.0 mol of Fe reacts completely with 0.65 mol of $O_2$ to give a mixture of only $FeO$ and $F{e}_2{O}_3$. The mole ratio of ferrous oxide to ferric oxide is

• A. 2 : 2
• B. 4 : 2
• C. 1 : 2
• D. 2 : 7

Answer 1

The correct option is B 4 : 2

Let moles of $FeO$ and $F{e}_2{O}_3$ in the mixture is a and b respectively, then by POAC we get following two equation.
$a+3b=0.65\times 2=1.3\dots \dots \left(i\right)$
$a+2b=1\dots \dots \left(ii\right)$
by solving (i) and (ii) we get a : b = 4 : 3