Solid state practice · Easy

Option D (1) is correct because in a simple cubic unit cell, there is one atom at each of the eight corners, and each corner atom contributes 1/8 to the unit cell, resulting in a total of 1 atom per unit cell (8 x 1/8 = 1).

Correct Answer + Core Reason: Option A (Frenkel defect) is correct because a Frenkel defect involves an ion leaving its lattice site and occupying an interstitial position.

Option D (All of the above) is correct because ferrites possess the formula AB2O4, have a spinel structure, and MgAl2O4 is an example of a ferrite.

Option B (8) is correct because in the fluorite structure (CaF₂), each Ca²⁺ ion is surrounded by 8 F⁻ ions, giving it a coordination number of 8.

Option B (Tetragonal system) is correct because $\mathrm{Ti}{\mathrm{O}_2}$ (Titanium dioxide) has a tetragonal crystal structure.

Option C (1) is correct because in a cubic close-packed structure, the number of octahedral voids is equal to the number of atoms.

Option B (Tetragonal) is correct because the tetragonal crystal system is defined by $a = b \ne c$ and $\alpha = \beta = \gamma = 90^\circ$.

Option B ($\uparrow \mathrm{ } \downarrow \mathrm{ } \uparrow \mathrm{ } \downarrow$) is correct because anti-ferromagnetism arises from the alignment of magnetic moments in opposite directions, resulting in a net magnetic moment of zero.

Option D (23) is correct because a cubic crystal possesses 23 elements of symmetry.

Option A (Ionic crystal) is correct because Zinc Sulfide (ZnS) is a compound formed by ionic bonding between zinc and sulfur ions, resulting in an ionic crystal structure.

Option D ($\uparrow , \downarrow , \uparrow , \downarrow , \uparrow , \downarrow$) is correct because in antiferromagnetic substances, the magnetic moments are aligned in an antiparallel manner, resulting in a net magnetic moment of zero.

Option D is correct because in the rock salt structure, Na+ ions occupy the octahedral voids, and Cl- ions form the ccp lattice; tetrahedral voids are not occupied by either.

Option D (8) is correct because in a diamond structure, carbon atoms occupy FCC lattice points and half of the tetrahedral voids, resulting in a total of 8 carbon atoms per unit cell.

Option C is correct because a face-centered cubic (fcc) unit cell contains 4 atoms: 1 from the corners (8 corners x 1/8 atom per corner) and 3 from the faces (6 faces x 1/2 atom per face).

Option C (F-centre) is correct because the appearance of color in solid state of alkali metal halides is due to F-centers, which are electrons trapped in anion vacancies.

Option A is the incorrect statement because Frenkel defects are favored when there is a significant size difference between cations and anions, not when they are almost equal.

Option C (1) is correct because in a cubic close-packed (ccp) structure, the number of octahedral voids is equal to the number of atoms.

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 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 ($\alpha = \beta = \gamma = {90^0}$) 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 C (Quartz) is correct because Quartz ($\mathrm{SiO}_2$) forms a giant network of covalently bonded atoms, making it a covalent crystal.

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

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