In a face centred cubic arrangement of A and B atoms in which 'A' atoms are at the corners of the unit cell and 'B atoms are at the face centres. One of the 'A' atoms is missing from one corner in unit cell.The simplest formula of compounds is

• A₇B₈

• A₇B₃

• AB₃

• A₇B₂₄

The ionic radii of Rb⁺ and I^- are 1.46 Å and 2.16 Å. The most probable type of structure exhibited by it is :

• CsCl type

• ZnS type

• NaCl type

• CaF₂ type

The correct statement regarding defect in solids is

• Frenkel defect is usually favoured by a very small difference in the sizes of cations and anions.

• Frenkel defect is a dislocation defect

• Trapping of proton in the lattice leads to the formation of F-centres.

• Schottky defect has no effect on the physical properties of solids.

Which of the following crystal has unit cell such that a≠b≠c and α≠β≠γ≠ 90°?

• NaNO₃

• K₂SO₄

• KNO₃

• K₂Cr₂O₇

A solid is made of two elements X and Z. The atoms Z are in CCP arrangement while the atom X occupy all the tetrahedral sites. What is the formula ofthe compound ?

• XZ

• XZ₂

• X₂Z

• X₂Z₃

Doping of Silicon (Si) with boron(B) leads to :

• n-type semiconductor

• p-type semiconductor

• metal

• insulator

Iodine is a:

• electrovalent solid

• atomic solid

• molecular solid

• covalent solid

Lattice energy of a solid increases if :

• size of ions are small

• charges of ions are small

• ions are neutral

• None of the above

119.

How many unit cells are present in a cube shaped ideal crystal of NaCl of mass 1.00 gm? [Atomic masses : Na = 23; Cl = 35.5]

• 2.57 × 10²¹

• 5.14 × 10²¹

• 1.28 × 10²¹

• 1.71 × 10²¹

Metals are good conductors of electricity because they contains:

• ionic bond

• a network structure

• very few valence element

• free electron