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Solid State · Question 11

NEET 2018MCQMedium📈 Topic in 12% papers+4−1
1

Iron exhibits bcc structure at room temperature. Above 900°C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900°C (assuming molar mass and atomic radii of iron remains constant with temperature) is

  1. 3 2
  2. 4 33 2
  3. 3 34 2
  4. 12

Answer

(3) 3 34 2

Solution

Density d = Z Ma3 NA ⇒ d Za3 (M and NA constant)

bcc: Z = 2, a = 4r 3

fcc: Z = 4, a = 2 2 r

⇒ dbccdfcc = 2 ( 4r 3 )3 (2 2 r )34

= 2 3 364 16 24

= 3 3 28

= 3 34 2

Answer: (3)

Out of syllabusNEET 2018

Keep practising — Solid State

2

Which is the incorrect statement?

  1. Density decreases in case of crystals with Schottky defect.
  2. NaCl(s) is insulator, silicon is semi conductor, silver is conductor, quartz is piezoelectric crystal.
  3. Frenkel defect is favoured in those ionic compounds in which sizes of cation and anions are almost equal
  4. FeO0.98 has non-stoichiometric metal deficiency defect.
Out of syllabusNEET 2017
3

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. (NA = 6.02 1023 mol-1)

  1. 527 pm
  2. 264 pm
  3. 154 pm
  4. 352 pm
Out of syllabusNEET 2016 (Phase 1)
4

The ionic radii of A+ and B- ions are 0.98 10-10 m and 1.81 10-10 m. The coordination number of each ion in AB is

  1. 8
  2. 2
  3. 6
  4. 4
Out of syllabusNEET 2016 (Phase 1)
5

In calcium fluoride, having the fluorite structure, the coordination numbers for calcium ion ( Ca2+) and fluoride ion (F-) are

  1. 4 and 2
  2. 6 and 6
  3. 8 and 4
  4. 4 and 8
Out of syllabusNEET 2016 (Phase 2)
6

The vacant space in bcc lattice unit cell is

  1. 48%
  2. 23%
  3. 32%
  4. 26%
Out of syllabusAIPMT 2015
7

The correct statement regarding defects in crystalline solids is

  1. Frenkel defects decrease the density of crystalline solids
  2. Frenkel defect is a dislocation defect
  3. Frenkel defect is found in halides of alkali metals
  4. Schottky defects have no effect on the density of crystalline solids
Out of syllabusAIPMT 2015
8

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?

  1. 80 pm
  2. 108 pm
  3. 40 pm
  4. 127 pm
Out of syllabusAIPMT 2015 (Cancelled)
9

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

  1. 2 3a
  2. 4 3a
  3. 34a
  4. 32a
Out of syllabusAIPMT 2014
10

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 (NA Avogadro's constant = 6.02 1023 mol-1)

  1. 27 g mol-1
  2. 20 g mol-1
  3. 40 g mol-1
  4. 30 g mol-1
Out of syllabusNEET 2013
11

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

  1. 6
  2. 1
  3. 4
  4. 8
Out of syllabusNEET 2013

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