solid state 2

The packing efficiency in simple, fcc, bcc unit cells will be respectively

• 74% 52.4% 68%

• 52.4% 68% 74%

• 68% 74% 52.4%

• 52.4% 74% 68%

The relationship between the atomic radius (r) and edge length (a) of a simple, fcc, bcc cubic unit cell will be respectively

• $\frac{a}{2}$ $\frac{\sqrt{2}a}{4}$ $\frac{\sqrt{3}a}{4}$

• $\frac{a}{2}$ $\frac{\sqrt{3}a}{4}$ $\frac{\sqrt{2}a}{4}$

• $\frac{\sqrt{2}a}{4}$ $\frac{\sqrt{3}a}{4}$ $\frac{a}{2}$

• $\frac{\sqrt{3}a}{4}$ $\frac{a}{2}$ $\frac{\sqrt{3}a}{4}$

The coordination number in simple, fcc, bcc close packing arrangement will be respectively

• 1, 4, 2

• 6, 12, 8

• 4, 6, 8

• none of the above

The total number of tetrahedral voids and octahedral voids in a given cubic unit cell with N number of atoms will be respectively

• 2N and N

• N and 2N

• 4N and N

• N and 4N

In METAL EXCESS DEFECTS the sites where an electron gets trapped in the anionic vacancy disturbing the ratio of cation to anion is known as

• E- CENTRE

• F- CENTRE

• G- CENTRE

• I- CENTRE

The total number of tetrahedral voids and octahedral voids per unit cell of face-centred cell (fcc) are

• 8, 4

• 4, 8

• 2, 4

• 4, 2

The relationship between the radius (r) of the tetrahedral void and the radius (R) of the atoms in close packing is

• r = 0.155 R

• r = 0.225 R

• r = 0.414 R

• r = 0.732 R

The relationship between the radius (r) of the octahedral void and the radius (R) of the atoms in close packing is

• r = 0.155 R

• r = 0.225 R

• r = 0.414 R

• r = 0.732 R

Which of the following statements about crystals is incorrect?

• The shape of a crystal is dependent on the chemical conditions under which it formed

• There are seven large groups of crystal geometries or crystal systems.

• There are many geometric planes in a single crystal.

• The atomic structure of a crystal defines it's geometric shape.

• The shape of a crystal is independent of the physical conditions under which it formed.

Schottky defect is observed in crystals when

• some cations move from their lattice site to interstitial sites

• equal number of cations and anions are missing from the lattice

• some lattice sites are occupied by electrons

• some imurity is present in the lattice