Which from following pair of compounds exhibits isomorphism?

Calculate the volume occupied by a particle in fcc unit cell if volume of unit cell is $1.6 \times 10^{-23} \mathrm{~cm}^3$.

Identify the type of defect in brass alloy.

Calculate the number of atoms present in 1 g of an element if it forms fcc unit cell structure. $\left[\rho \times \mathrm{a}^3=6.8 \times 10^{-22} \mathrm{~g}\right]$