$\mathrm{KCl}$ crystallizes in the same type of unit cells as $\mathrm{NaCl}$. The ionic radius of ${\mathrm{Na}}^{+}$ is $0.5$ times that of ${\mathrm{Cl}}^{-}$and $0.7$ times that of ${\mathrm{K}}^{+}$. Calculate

a) the ratio of the side of unit cells of $\mathrm{KCl}$ to $\mathrm{NaCl}$,

b) the ratio of the density of $\mathrm{NaCl}$ to $\mathrm{KCl}$.

The cubic unit cell structure of a compound containing cation $\mathrm{M}$ and anion $\mathrm{X}$ is shown below. When compared to the anion, the cation has smaller ionic radius. Choose the correct statement(s).

In the following circuit diagram, the current through the battery is

Match the following

        List - I                                      List-II
A) Metallic solid                         I) Carbon tetrachloride
B) Covalent solid                       II) Calcium fluoride
C) Molecular solid                     III) Copper
D) Ionic solid                             IV) Silicon carbide
                                                   V) Glass

The correct answer is