2022Flame Institute

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.

a. 154 pm b. 352 pm c. 527 pm d. 264 pm Ans. b (18)

Ferrous oxide has a cubic structure and each edge of the unit cell is

50 Å . Assuming density of the oxide as 4.0g – cm -3 then the number of Fe2+ and O2- ions present in each unit cell will be a. Four Fe2+ and four O2- b. Two Fe2+ and four O2- …

The second order Bragg’s diffraction of X – rays with

λ = 1 Å from a set of parallel planes in a metal occurs at an angle of 60º . The distance between the scattering planes in the crystal is a. 0.575 Å b. 1.00 Å c. 2.00Å d. 1.15 …

Percentage of the free space in cubic close packed structure and in body centered packed structure are respectively

a. 48 % and 26 % b. 30 % and 26 % c. 26 % and 32 % d.32% and 48 % Ans. c (11)

The edge length of unit cell of a metal having molecular weight 75g/mol is

5 Å which crystallize in cubic lattice. If the density is 2g/ cc then find the radius of metal atoms. (N A = 6 x 10 23 ) Give the answer in pm a. 217 pm b. 210 pm c. 220 …

How many unit cells are present in a cubic shaped ideal crystal of NaCl of mass 1.00g [ Atomic masses : Na = 23, Cl = 35.5]

a. 2.57 x 10 21 unit cells b. 5. 14 x 1021 unit cells c. 1.28 x 10 21 unit cells d. 1. 71 x 1021 unit cells Ans. a (5)

In orthorhombic, the value of a, b and c are respectively

4.2 Å 8.6 Å and 8.3 Å given the molecular mass of the solute is 155 g mol -1 and that of density is 3.3 g/ cc, the number of formula units per unit cell is a. 2 b. 3 c. …

The pyknometric density of sodium chloride crystal is

2.165 x 103 kg m -3 while its X – rays density is 2.178 x 103 kg m -3 . The fraction of unoccupied sites in sodium chloride crystal is a. 5. 96 x 10-3 b. 5.96 c. 5.96 x 10-2 d. …

When an electron in an excited Mo atom fall from L to K shell; an X- ray is emitted. These X-rays are diffracted at angles of 7.75° by planes with a separation of

2.64Å. What is the difference in energy between K- shell an L – shell in Mo assuming a first-order diffraction (sin 7.75° = 0.1349) a. 36.88 x 10-19 j b. 27.88 x 10 10-16 j c. 63. 88 x 10 10-17 …

To obtain a diffraction peak, for a crystalline solid with inter plane distance equal to the wavelength of incident X-ray radiation, the angle of incidence should be

a. 90° b. 0° c. 30° d. 60 ° Ans. c (6)

If the angle of incidence of X-ray of wavelength 3 Å which produces a second order diffracted beam from the (100) plane in a simple cubic lattice with interlayer spacing a = 6 Å is 30°, the angle of incidence that produce a first order diffracted beam from the (200) planes is

a. 15° b. 45° c. 30° d. 60° Ans. c (16)

10 mL of 1 m M surfactant solution forms a monolayer convering 0.24 cm^2 on a polar substance. If the polar head is approximated as a cube, which is its edge length

a. 1.0 pm b. 2. 0 nm c. 0.1 nm d. 2.0 pm Ans. d (24)

An element has a face-centred cubic (fcc) structure with a cell edge of a. The distance between the centres of two nearest tetraheadral voids in the lattice is

a. √2a b. a c. 3/2 (a) d. a/2 Ans. d Explanation : Nearest distance between tetrahedral voids in a fcc lattice is a/2 (42)

8. If a rubber ball is taken at the depth of 200 m in a pool, its volume decreases by 0.1%.

If the density of the water is 1× 103 Kg/m3 and g=10 m/s 2, then the volume elasticity in (N/m2) will be (a) 108 …

The correct statement for the molecule,

Csl 3 , is a. It is covalent molecule b. it contains Cs3+ and I –3 c. It contains Cs+ and I –3 ions d. It contains Cs+ , I – and lattice I – molecule Ans. b (13)

Which of the following statements is correct for CsBr3

a. It is covalent compound b. it contains Cs3+ and Br – ions c. It contains Cs+ and Br3– ions d. It contains Cs+ , Br– and lattice Br 2 molecule Ans. c (6)

KCl crystallises in the same type of lattice as does NaCl. Given that

r Na + / r Cl – = 0.55 and r k+ / r Cl– = 0. 74. Calculate the ratio of the side of the unit cell for KCl to that of NaCl a. 1.123 b. 0.891 c. 1.414 …

If the unit cell of a mineral has cubic close packed array of oxygen atoms with m fraction of octahedral holes occupied by aluminium ions and n fraction of tetrahedral holes occupied by magnesium ions, m and n respectively are

a. 1/2 , 1/ 8 b. 1 , 1/4 c. 1/2 , 1/ 2 d. 1/4 , 1/ 8 Ans. a (8)

A metal crystallizers into a lattice containing a sequence of layers of atoms of ABABAB… What percentage by volume of this lattice has empty space

a. 74 b. 26 c. 20 d. 16 Ans. b Explanation : ABAB… is hexagonal close packing in which space occupied = 74 % and empty space = 26 (5)

Structure of a mixed oxide is cubic close- packed . The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by a monovalent metal B. The formula of the oxide is

a. ABO 2 b. A 2BO2 c. A2 B3 O4 d. AB 2 O 2 Ans. d (15)

If Agl crystallises in zinc blende structure with

I– ions at lattice points. What fraction of tetrahedral voids is occupied by Ag + ions a. 25 % b. 50 % c. 100 % d. 75 % Ans. b (4)

In a compound atoms of Y form ccp lattice and those of element X occupy 2/3rd of tetrahedral voids. The formula of the compound will be

a. X2 Y3 b. X2 Y c. X 3 Y 4 d. X 4 Y 3 Ans. d (7)

The

Ca2+ and F – are located in CaF 2 crystal respectively at face centred cubic lattic points and in a. Tetrahedral voids b. Half of tetrahedral voids c. Octahedral voids d. Half of octahedral voids Ans. a (6)

Hexagonal close packing is found in crystal lattice of

a. Na b. Mg c. Al d. None of these Ans. b Explanation : Coordination number in hcp = 12 Coordination number in Mg is also = 12 (7)

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

a. XZ b. XZ2 c. X 2 Z d. X 2 Z 3 Ans. c Explanation : Tetrahedral sites are double comparable to octahdral sites then ration of X and Z respectively 2 : 1 since formula of the compound X 2 …

In which of the following crystals alternate tetrahedral voids are occupied

a. NaCl b. ZnS c. CaF2 d. Na 2 O Ans. b (13)

The number of octahedral sites per sphere in a fcc structure is

a. 8 b. 4 c. 2 d. 1 Ans. d Explanation : Number of octahedral sites = Number of sphere in the packing Number of octahedral sites per sphere = 1 (9)

The intermetallic compound LiAg crystallizes in cubic lattice in which both lithium and silver have coordination number of eight. The crystal class is

a. Simple cube b. Body centred cube c. Face- centred cube d. None of these Ans. b (10)

In an antifluorite structure, cations occupy

a. Octahedral voids b. Centre of cube c. Tetrahedral voids d. Corners of cube Ans. c Explanation : In antifluorite structure the oxide ions form a face – centered cubic array and the metal ions (cations) fill half the tetrahedral …

Which is not the correct statement for ionic solids in which positive and negative ions are held by strong electrostatic attractive forces

a. The radius r + / r – increase as coordination number increases b. As the difference in size of ions increases, coordination number increases c. When coordination number is eight the r + / r – ratio lies between 0.225 to 0.414 d. …

Suppose the mass of a single Ag atomm is ‘m’ . Ag metal crystallizes in fcc lattice with unit cell of length ‘a’ . The density of Ag metal in terms of ‘a’ and ‘m’ is

a. 4m/a 3 b. 2m/ a 3 c. m/a 3 d. m/ 4a 3 Ans. a (7)

The correct order of the packing efficiency in different types of unit cells is..

a. fcc < bcc < simple cubic b. fcc > bcc >simple cubic c. fcc < bcc > simple cubic d. fcc < bcc > simple cubic Ans. b (15)

Which of the following statement in not true about the hexagonal close packing

a. The coordination number is 12 b. It has 74% packing efficiency c. Tetrahedral voids of the second layer are coverd by the spheres of the third layer d. In this arrangement spheres of the fourth layer are exactly aligned …