Which of the following molecular formula and type of defect are correct for the following statement? "In…
Which of the following molecular formula and type of defect are correct for the following statement?
"In $\mathrm{FeO}$ crystal, some $\mathrm{Fe}^{2+}$ ions are missing and the loss of positive charge is made up by the presence of $\mathrm{Fe}^{3+}$ ions".
$\mathrm{Fe}_{0.95} \mathrm{O}$ and metal excess defect.
$\mathrm{Fe}_{1.05} \mathrm{O}$ and metal deficiency defect.
$\mathrm{Fe}_{0.95} \mathrm{O}$ and metal deficiency defect.
$\mathrm{Fe}_{1.05} \mathrm{O}$ and metal excess defect.
Solution
The crystal of FeO shows metal deficiency defect because some $\mathrm{Fe}^{2+}$ ions go missing from their position in lattice and the loss of positive charge is made up by the presence of required number of $\mathrm{Fe}^{3+}$ ions. Usually around $15 \% \mathrm{Fe}^{2+}$ ions are found missing, therefore, the formula of oxide of iron is $\mathrm{Fe}_{0.95} \mathrm{O}$.