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

In the laboratory,sodium chloride is made by burning sodium in an atmosphere of chlorine. The resulting crystal is yellow in color. The cause of this yellow color is:

The formula of nickel oxide with metal deficiency defect in its crystal is $Ni_{0.98}O$. The crystal contains $Ni^{2+}$ and $Ni^{3+}$ ions. The fraction of nickel existing as $Ni^{2+}$ ions in the crystal is

While writing the formula of ferrous oxide,it is written as $(FeO)$,because it is

When $Fe_{0.93}O$ is heated in the presence of oxygen,it converts to $Fe_2O_3$. The number of correct statement$(s)$ from the following is:
$A.$ The equivalent weight of $Fe_{0.93}O$ is $\frac{\text{Molecular weight}}{0.79}$.
$B.$ The number of moles of $Fe^{2+}$ and $Fe^{3+}$ in $1 \text{ mole}$ of $Fe_{0.93}O$ is $0.79$ and $0.14$ respectively.
$C.$ $Fe_{0.93}O$ is metal deficient with a lattice comprising of a cubic closed-packed arrangement of $O^{2-}$ ions.
$D.$ The $\%$ composition of $Fe^{2+}$ and $Fe^{3+}$ in $Fe_{0.93}O$ is $85\%$ and $15\%$ respectively.

Which of the following point defects are shown by $AgBr_{(s)}$ crystals?
$A$. Schottky defect
$B$. Frenkel defect
$C$. Metal excess defect
$D$. Metal deficiency defect