Question 1

Which one of the following statements about the zeolites is false?

Accepted Answer

Some of the SiO4⁴⁻ units are replaced by AlO4⁵⁻ and AlO6⁵⁻ ions in zeolites. Zeolites are aluminosilicates where some SiO4⁴⁻ units are replaced by AlO4⁵⁻ ions, but not AlO6⁵⁻ ions. The statement mentioning AlO6⁵⁻ is incorrect.

Question 2

Glass is a:

Accepted Answer

Supercooled liquid. Glass is considered a supercooled liquid because it lacks a crystalline structure and exhibits properties of an amorphous solid.

Question 3

When electrons are trapped into the crystal in anion vacancy, the defect is known as

Accepted Answer

F-centres. When electrons are trapped in anion vacancies, they create F-centres, which impart color to the crystal. This is a specific type of defect in the crystal lattice.

Question 4

On doping Ge metal with a little of In or Ga, one gets

Accepted Answer

p-type semi conductor. When Ge (a group 14 element) is doped with In or Ga (group 13 elements), it introduces holes as the majority charge carriers, forming a p-type semiconductor.

Question 5

For two ionic solids CaO and KI, identify the wrong statement amongst the following:

Accepted Answer

KI has higher melting point. The melting point of CaO is higher than that of KI due to stronger ionic bonds in CaO, as it involves divalent ions (Ca²⁺ and O²⁻) compared to monovalent ions (K⁺ and I⁻) in KI. Thus, option C is incorrect.

Question 6

An example of a double salt is

Accepted Answer

Potash Alum. Double salts are compounds that dissociate into their constituent ions in solution. Potash alum (KAl(SO4)2·12H2O) is a classic example of a double salt.

Question 7

The ability of a substance to assume two or more crystalline structures is called

Accepted Answer

Polymorphism. Polymorphism refers to the ability of a substance to exist in two or more different crystalline forms. This is a property of certain solids.

Question 8

The pure crystalline substance on being heated gradually first forms a turbid liquid at constant temperature and still at higher temperature turbidity completely disappears. The behaviour is a characteristic of substance forming

Accepted Answer

Liquid crystals. The described behavior, where a crystalline substance transitions to a turbid liquid and then to a clear liquid upon heating, is characteristic of liquid crystals. These substances exhibit properties of both liquids and solids in specific temperature ranges.

Question 9

A solid compound XY has NaCl structure. If the radius of the cation is 100 pm, the radius of the anion (Y⁻) will be:

Accepted Answer

241.5 pm. In the NaCl structure, the radius ratio (r+/r−) for cation to anion is approximately 0.414 for stable coordination. Given the cation radius is 100 pm, the anion radius can be calculated as r− = r+/0.414 = 100/0.414 ≈ 241.5 pm.

Question 10

The pycnometric density of sodium chloride crystal is 2.165 × 10³ kg m⁻³ while its X-ray density is 2.178 × 10³ kg m⁻³. The fraction of unoccupied sites in sodium chloride crystal is

Accepted Answer

5.96 × 10⁻³. The fraction of unoccupied sites is calculated using the formula: (X-ray density - Pycnometric density) / X-ray density. Substituting the given values, (2.178 × 10³ - 2.165 × 10³) / 2.178 × 10³ = 5.96 × 10⁻³.

Question 11

In the solid state, MgO has the same structure as that of sodium chloride. The number of oxygens surrounding each magnesium in MgO is

Accepted Answer

6. In the NaCl structure, each cation is surrounded by six anions in an octahedral arrangement. Similarly, in MgO, each magnesium ion is surrounded by six oxygen ions.

Question 12

When molten zinc is converted into solid state, it acquires hcp structure. The number of nearest neighbours will be

Accepted Answer

12. In an hcp (hexagonal close-packed) structure, each atom is surrounded by 12 nearest neighbors due to its efficient packing arrangement.

Question 13

A compound is formed by cation C and anion A. The anions form hexagonal close packed (hcp) lattice and the cations occupy 75% of octahedral voids. The formula of the compound is:

Accepted Answer

C3A2. In an hcp lattice, the number of anions (A) is equal to the number of lattice points, i.e., 1. The number of octahedral voids is also equal to the number of lattice points. Since 75% of octahedral voids are occupied by cations (C), the ratio of cations to anions is 3:2, giving the formula C3A2.

Question 14

Iron exhibits bcc structure at room temperature. Above 900°C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900°C (assuming molar mass and atomic radii of iron remains constant with temperature) is:

Accepted Answer

√3/√2. The density ratio depends on the packing efficiency of the structures. For bcc, the packing efficiency is 68%, and for fcc, it is 74%. The ratio of densities is proportional to the ratio of packing efficiencies, which simplifies to √3/√2.

Question 15

Most crystals show good cleavage because their atoms, ions or molecules are

Accepted Answer

arranged in planes. Crystals exhibit good cleavage because their atoms, ions, or molecules are arranged in planes, allowing them to break along these planes more easily.

Question 16

An element has a body centered cubic (bcc) structure with a cell edge of 288 pm. The atomic radius is:

Accepted Answer

√3/4 × 288 pm. In a body-centered cubic (bcc) structure, the relationship between the atomic radius (r) and the edge length (a) is r = √3/4 × a. Substituting a = 288 pm, the atomic radius is √3/4 × 288 pm.

Question 17

The number of carbon atoms per unit cell of diamond unit cell is:

Accepted Answer

8. Diamond has a face-centered cubic (FCC) structure with 8 carbon atoms per unit cell, considering the contribution of atoms at corners, faces, and inside the cell.

Question 18

Structure of a mixed oxide is cubic close-packed (c.c.p). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are occupied by monovalent metal B. The formula of the oxide is:

Accepted Answer

A₂B₃O₄. In a c.c.p. structure, the number of oxide ions (O²⁻) per unit cell is 4. The number of tetrahedral voids is twice the number of oxide ions, i.e., 8, and one-fourth of these are occupied by A²⁺, giving 2 A²⁺ ions. The number of octahedral voids equals the number of oxide ions, i.e., 4, and all are occupied by B⁺ ions. Thus, the formula is A₂B₄O₄, which simplifies to A₂B₃O₄.

Question 19

A metal crystallizes with a face-centered cubic lattice. The edge length of the unit cell is 408 pm. The diameter of the metal atom is:

Accepted Answer

288 pm. In a face-centered cubic (FCC) lattice, the relation between the edge length (a) and the atomic radius (r) is given by: a = 2√2r. Substituting a = 408 pm, we get r = 144 pm. The diameter is 2r = 288 pm.

Question 20

AB crystallizes in a body centered cubic lattice with edge length ‘a’ equal to 387 pm. The distance between two oppositely charged ions in the lattice is:

Accepted Answer

335 pm. In a body-centered cubic lattice, the distance between two oppositely charged ions is half the body diagonal. The body diagonal is √3a, so the distance is (√3a)/2. Substituting a = 387 pm, the distance is (√3 × 387)/2 = 335 pm.

NEET Chemistry: The Solid State questions with solutions

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