Point defects are present in

Experimentally,it was found that a metal oxide has the formula $M_{0.98}O$. The metal $M$ is present as $M^{2+}$ and $M^{3+}$ in its oxide. The fraction of the metal which exists as $M^{3+}$ would be: .................... $\%$

When $KCl$ is heated in an atmosphere of $K$ vapor,it appears violet. This is because .................

The correct statement among the following,regarding defects in solids is:
$(1)$ Frenkel defect is favored by small difference in the sizes of cation and anion.
$(2)$ Frenkel defect is a metal excess defect.
$(3)$ Trapping of electron in the lattice leads to formation of $F$-centres.
$(4)$ Schottky defect has no effect on the physical property of solids.

Calculate the percentage of $Fe^{+2}$ in $Fe_{0.95}O$.

Schottky defect in crystals is observed when