The statement that is INCORRECT about the interstitial compounds is :

• they are chemically reactive

• they have metallic conductivity

• they have high melting points

• they are very hard

Consider the bcc unit cells of the solids 1 and 2 with the position of atoms as shown below. The radius of atom B is twice that of atom A. The unit cell edge length is 50% more in solid 2 than in 1. What is the approximate packing efficiency in solid 2?

• 75%

• 65%

• 45%

• 90%

143.

Lithium has a bcc structure. Its density is 530 kg m^-3 and its atomic mass is 6.94 g mol^-1. Calculate the edge length of a unit cell of lithium metal. (N_A = 6.02 x 10²³ mol^-1).

• 352pm

• 527pm

• 264pm

• 264pm

A given metal crystallises out with a cubic structure having edge length of 361 pm. If there are four metal atoms in one unit cell, what is the radius of one atom.

• 40 pm

• 127 pm

• 80 pm

• 80 pm

If a is the length of the side of a cube, the distance between the body centred atom and one corner atom in  the cube will be

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

• 4

• 8

• 6

• 6

A metal has a fcc lattice. The edge length of the unit cell is 404 pm. The density of the metal is 2.72 g cm^-3. The molar mass of the metal is (N_A Avogadro's constant= 6.02 x 10²³ mol^-1)

• 40 g mol^-1

• 30 g mol^-1

• 27 g mol^-1

• 27 g mol^-1

Which of the following statements about the interstitial compounds is incorrect?

• They retain metallic conductivity

• They are chemically reactive

• They are much harder than the pure metal

• They are much harder than the pure metal

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

• 288 pm

• 408 pm

• 144 pm

• 204 pm

The number of octahedral voids (s) per atom present in a cubic close-packed structure is 

• 1

• 3

• 2

• 4