NCERT Class XII Chemistry
Chapter - The Solid State
Questions with Solutions
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Question : 44
Total: 50
An element with molar mass 2.7 × 10 – 2 kg mol– 1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 × 10 3 kg m– 3 , what is the nature of the cubic unit cell?
Solution:
Given M (molar mass of the element) = 2.7 × 10 – 2 kg mol– 1
a (edge length) = 405 pm= 405 × 10 – 12 m = 4.05 × 10 – 10 m
d (density)= 2.7 × 10 3 kg m– 3
N A (Avogadro’s number) = 6.022 × 10 23 mol– 1
Using formula,
Density (d)=
or, Z =
or, Z=
= 4
Number of atoms of the element present per unit cell = 4. Hence, the cubic unit cell must be face-centred or cubic close packed (ccp).
a (edge length) = 405 pm
d (density)
Using formula,
Density (d)
or, Z
Number of atoms of the element present per unit cell = 4. Hence, the cubic unit cell must be face-centred or cubic close packed (ccp).
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