The diffraction of barium with X-radiation of wavelength 2.29Å gives a first – order reflection at 30°. What is the distance between the diffracted planes.

(1) 3.29 Å

(2) 4.39 Å

(3) 2.29 Å

(4) 6.29 Å

The vacant space in bcc lattice cell is ;

1. 26%

2. 48%

3. 23%

4. 32%

Copper crystallises in a face-centred cubic lattice with a unit cell length of 361 pm. What

is the radius of copper atom in pm?

1. 128

2. 157

3. 181

4. 108

Lithium metal crystallises in a body centred cubic crystal. If the length of the side of the

unit cell of lithium is 351 pm, the atomic radius of the lithium will be

1. 240.8 pm

2. 151.8 pm

3. 75.5 pm

4. 300.5 pm

If 'a' stands for the edge length of the cubic systems: simple cubic, body centered cubic and face centered cubic, then the ratio of radii of the spheres in these systems will be respectively,

$\left(\mathrm{a}\right)<mspace\; width="1em"></mspace>\frac{1}{2}\mathrm{a}:<mspace\; width="1em"></mspace>\frac{\sqrt{3}}{4}\mathrm{a}:\frac{1}{2\sqrt{2}}\mathrm{a}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\left(\mathrm{b}\right)<mspace\; width="1em"></mspace>\frac{1}{2}\mathrm{a}:\sqrt{3}\mathrm{a}:\frac{1}{\sqrt{2}}\mathrm{a}$
$\left(\mathrm{c}\right)<mspace\; width="1em"></mspace>\frac{1}{2}\mathrm{a}:\frac{\sqrt{3}}{2}\mathrm{a}:\frac{\sqrt{2}}{2}\mathrm{a}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>\left(\mathrm{d}\right)<mspace\; width="1em"></mspace>1\mathrm{a}:\sqrt{3}\mathrm{a}:\sqrt{2}\mathrm{a}$

Which of the following statements is not correct?

CsBr has a (bcc) arrangement and its unit cell edge length is 400 pm. Calculate the interionic distance in CsBr.

(1) 346.4 pm

(2) 643 pm

(3) 66.31 pm

(4) 431.5 pm

Lithium borohydride $\left(LiB{H}_4\right),$crystallises in an orthorhombic system with 4 molecules per unit cell. The unit cell dimensions are : a = 6.81Å, b= 4.43Å, c=7.17Å. If the molar mass of $LiB{H}_4$ is 21.76 g mol^–1. The density of the crystal is –

(1) 0.67 g cm^–3

(2) 0.58  g cm^–3

(3) 1.23 g cm^–3

(4) 6.68  g cm^–3

From the fact that the length of the side of a unit cell of lithium is 351 pm. Calculate its

atomic radius. Lithium forms body-centered cubic crystals.

(1) 152.69 pm

(2) 62.71 pm

(3) 151.98 pm

(4) 54.61 pm

Silver metal crystallises in a cubic closest – packed arrangement with the edge of the unit cell having a length a = 407 pm. What is the radius of silver atom.

(1) 143.9 pm

(2) 15.6 pm

(3) 11.59 pm

(4) 13.61 pm