Class 12 Chemistry Eng / Crystal Structure part 2

Solid Xe has a crystal structure built on fcc unit cells. If Xe atom has a radius of 219.2pm, then the length of the face-diagonal of the unit cell in its crystal is-

• 438.4 pm

• 657.6 pm

• 876.8 pm

• 763.2 pm

Each side of the unit cell of NaCl crystal has a length of 552 pm. If radius of Na⁺ be 95 pm, then radius of Cl^- is ..........

• 305pm

• 457pm

• 181pm

• 362pm

The crystal structure of an element is based on face-centered cubic unit cell with an edge length of : a' cm. The packing efficiency of a face-centered cubic unit cell is 74% . If each atom of the element has a volume of x' cm^{^3} then the relation between 'a' and 'x' is

• a = 1.27 * x ^1/3

• a = 2.05 * x ^1/3

• a = 1.75 * x ^1/3

• a = 1.84 * x ^1/3

An ionic compound AB crystallises in a body-centered cubic lattice. The unit cell of the lattice has an edge length of 387 pm. The closest distance between two oppositely charged ions in the crystal lattice is-

• 289.72pm

• 273.65pm

• 335.15pm

• 193.5pm

An element has a bcc unit cell with edge length of 2.88Å. If the element has a density of 7.2g cm^{^-3 .} Then the number of atoms in 103.6g of the element is ..........

• 6 * 10²³

• 1.2 * 10²⁴

• 2.8 * 10²²

• 4.7 * 10²²

Adding a very small amount of CdCl2 to the crystal lattice of AgCl results in a defect which is called as-

• Schottky defect

• interstitial defect

• metal excess defect

• impurity defect

Mg crystallises in hcp crystal structure. The total number of tetrahedral and octahedral holes in 0.25 mol of Mg is .............

• 1.505 * 10^23

• 7.525 * 10^22

• 3.01 * 10^23

• 4.517 * 10^23

For a particle of radius r to fit into the tetrahedral hole of a cubic close-packed structure of particles with radius R, without causing any distortion of the structure, it is necessary that the value of r should be-

• 0.225 times the value of R

• 4.415 times the value of R

• 2.415 times the value of R

• 2.225 times the value of R