Which of the following is $NOT$ a characteristic of Schottky defect?

As a result of Schottky defect,the density of the crystal:

Which of the following compounds is likely to show both Frenkel and Schottky defects in its crystalline form?

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.

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:

$A$ sample of ferrous oxide has actual formula $Fe_{0.93}O_{1.00}$. In this sample,what fraction of metal ions are $Fe^{2+}$ ions? What type of non-stoichiometric defect is present in this sample?