When $\mathrm{Fe_{0.93}O}$ is heated in presence of oxygen, it converts to $\mathrm{Fe_2O_3}$. The number of correct statement/s from the following is ________
A. The equivalent weight of $\mathrm{Fe_{0.93}O}$ is ${{\mathrm{Molecular\,weight}} \over {0.79}}$
B. The number of moles of Fe$^{2+}$ and Fe$^{3+}$ in 1 mole of $\mathrm{Fe_{0.93}O}$ is 0.79 and 0.14 respectively
C. $\mathrm{Fe_{0.93}O}$ is metal deficient with lattice comprising of cubic closed packed arrangement of O$^{2-}$ ions
D. The % composition of Fe$^{2+}$ and Fe$^{3+}$ in $\mathrm{Fe_{0.93}O}$ is 85% and 15% respectively
Solution
Let the number of $\mathrm{Fe}^{2+}$ ions be $x$ and number of $\mathrm{Fe}^{3+}$ ions be $0.93-x$.
<br/><br/>According to the charge neutrality,
<br/><br/>$$
\begin{aligned}
& 2 x+3(0.93-x)=2 \Rightarrow 2 x-3 x+2.79=2 \Rightarrow x=0.79 \\\\
& \mathrm{Fe}^{2+} \text { ion }=x=0.79 \\\\
& \mathrm{Fe}^{3+} \text { ion }=0.93-x=0.93-0.79=0.14 \\\\
& \% \text { of } \mathrm{Fe}^{2+} \text { ion }=\frac{0.79}{0.93} \times 100=84.95 \% \approx 85 \% \\\\
& \% \text { of } \mathrm{Fe}^{3+} \text { ion }=\frac{0.14}{0.93} \times 100=15.05 \%
\end{aligned}
$$
<br/><br/>As it is a metal deficiency defect,
<br/><br/>so, 1 mol of $\mathrm{Fe}_{0.93} \mathrm{O}$ contains $1 \mathrm{~mol}$ of oxide ions and $0.93 \mathrm{~mol}$ of iron ions as $\mathrm{Fe}^{2+}$ and $\mathrm{Fe}^{3+}$.
<br/><br/>So, moles of $\mathrm{Fe}^{2+}=0.79$
<br/><br/>and moles of $\mathrm{Fe}^{3+}=0.14$
<br/><br/>$$
\text { The equivalent weight }=\frac{\text { Molecular weight }}{n \text {-factor }}
$$
<br/><br/>$F{e^{2 + }} \to F{e^{3 + }} + {e^ - }$
<br/><br/>For one $\mathrm{Fe}^{2+}, n$-factor $=1$
<br/><br/>$\therefore $ For $0.79 \,\mathrm{Fe}^{2+}, n$-factor $=0.79$
<br/><br/>Out of $0.93 \mathrm{~mol}$, there are $0.79 \mathrm{~mol} \,\mathrm{Fe}^{2+}$ ions are present.
About this question
Subject: Chemistry · Chapter: Some Basic Concepts of Chemistry · Topic: Mole Concept
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