Solid state practice · Medium

Option A (48,32,26) is correct because the percentages of void space for simple cubic, body-centered cubic, and hexagonal close-packed arrangements are approximately 48%, 32%, and 26%, respectively.

Option B (4) is correct because in $N{a_2}O$, each $N{a^+}$ ion is coordinated to 4 oxide ions ($O^{2-}$).

Option B is correct because both the assertion and reason are true, but the reason doesn't explain the assertion. Stoichiometric compounds maintain a fixed ratio of elements, and Schottky/Frenkel defects don't change this ratio, but they are not the *reason* for the law of constant composition.

Option A ($1 \times {10^{ - 3}}mol\%$) is correct because each SrCl2 introduces one cation vacancy.

Option D (All are correct answer.) is correct because zinc and lead are immiscible in the molten state, forming separate layers, and silver is soluble in both zinc and lead.

Option D (6, 12, 8) is correct because the coordination numbers for simple cubic, FCC (face-centered cubic), and BCC (body-centered cubic) lattices are 6, 12, and 8, respectively.

Option C is correct. Covalent crystals have high melting points, but the reason that covalent bonds are stronger than ionic bonds is incorrect. The network structure is the main reason.

Option A ($5.783\mathop \mathrm{A}\limits^ \circ$) is correct because it is calculated using the density formula for a face-centered cubic structure.