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 is:

(Molar mass and atomic radii of iron remain constant with temperature) 

1. 32

2. 4332

3. 3342

4. 12

Subtopic:  Density & Packing Fraction |
 57%
From NCERT
NEET - 2018
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The incorrect statement among the following is -

1. Density decreases in case of crystals with Schottky's defect.
2. NaCl(s) is insulator, silicon is semiconductor, silver is conductor, quartz is piezo electric crystal.
3. Frenkel defect is favoured in those ionic compounds in which sizes of cations and anions have large difference.
4. \(Fe_{0.98}O\) has non stoichiometric metal excess defect.
Subtopic:  Imperfections in Solids & Semiconductors |
 53%
From NCERT
NEET - 2017
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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

Subtopic:  Voids, Radius Ratio & Coordination Number |
 71%
NEET - 2016
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Lithium has a bcc structure. Its density is 530 kg m-3 and its atomic mass is 6.94 g mol-1. The edge length of a unit cell of lithium metal is: 
(NA= 6.02 X 1023 mol-1)
1. 352 pm
2. 527 pm
3. 264 pm
4. 154 pm
Subtopic:  Density & Packing Fraction |
 57%
From NCERT
NEET - 2016
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The ionic radii of A+ and B- ions are 0.98 x10-10 m and 1.81 x10-10 m. The coordination number of each ion in AB is:
1. 8
2. 2
3. 6
4. 4
Subtopic:  Voids, Radius Ratio & Coordination Number |
 71%
NEET - 2016
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