Question

Fill in the blanks by choosing an appropriate option. A sample of ferrous oxide has actual formula $F{e}_{0.93}{O}_{1.00}.$ In this sample ______(i) fraction of metal ions are $F{e}^{+}$ ions. _______(ii) type of non-stoichiometric defect is present in this sample.

• A. (i) 0.849 (ii) Metal deficiency
• B. (i) 0.790 (ii) Metal deficiency
• C. (i) 0.145 (ii) Metal excess
• D. (i) 0.93 (ii) Vacancy defect

Answer 1

The correct option is A (i) 0.849 (ii) Metal deficiency

Given, sample of ferrous oxide is $F{e}_{0.93}{O}_{1.00}$.

Let number of $F{e}^{2+}$ ions is $x$ then number of $F{e}^{3+}$ ions is $(0.93-x)$

Now, for electrical neutrality, $(+2)x+(+3)(0.93-x)=+2$

$\Rightarrow 2x+2.79–3x=2$

$\Rightarrow x=0.79$

So, number of $F{e}^{2+}$ ions $=0.79$

Number of $F{e}^{3+}$ ions $=0.14$

So, fraction of $F{e}^{2+}$ ions $=\frac{0.79}{0.93}=0.849$

$FeO$ has non stochiometric metal deficiency defect in which number of $F{e}^{2+}$ ions are lesser than $O^{-}$ ions as compared to stochiometric formula. The neutrality is maintained to variable oxidation state possessing capability of $Fe$.