Solid state practice · Mixed difficulty

Option C (In calcium fluoride structure, coordination number of $Ca^{2+}$ is 4) is correct because the coordination number of $Ca^{2+}$ in $CaF_2$ is 8, not 4.

Option D (Solubility in polar solvents) is correct because ionic solids dissolve in polar solvents due to ion-dipole interactions.

Option D (Non – stoichiometric defects do not alter the density of the solid) is not true because non-stoichiometric defects involve either excess metal ions or metal deficiencies, which *do* alter the density of the solid.

The correct answer is A ($13.15 \mathrm{~M}$) because it is calculated using the density, percentage strength, and molar mass of HCl.

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 (Molecular solid) is correct because ice (solid water) consists of individual water molecules held together by intermolecular forces (hydrogen bonds), which is characteristic of molecular solids.

Option C (Glass) is correct because glass lacks a long-range ordered structure and is therefore an amorphous solid, unlike the other crystalline options.

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 B ($\alpha = \beta = \gamma = {90^0}$) is correct because the orthorhombic crystal system has axial ratios $a \ne b \ne c$ and all axial angles are equal to 90 degrees.

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

Option C (Quartz) is correct because Quartz ($\mathrm{SiO}_2$) forms a giant network of covalently bonded atoms, making it a covalent crystal.

Option A (Both (A) and (R) are correct and (R) is the correct explanation of (A)) is correct because the assertion is derived from the anion-anion contact in the LiCl structure.

Option A ($4\mathrm{ }K$) is correct because mercury becomes a superconductor at approximately 4K, meaning its resistance drops to almost zero.

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 A (Body centred cubic lattice) is correct because the CsCl crystal structure is a body-centered cubic lattice.

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.