NCERT Class XII Chemistry
Chapter - The Solid State
Questions with Solutions
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Question : 24
Total: 50
Aluminium crystallises in a cubic close packed structure. Its metallic radius is 125 pm.
(i) What is the length of the side of the unit cell?
(ii) How many unit cells are there in 1.00 cm3
(i) What is the length of the side of the unit cell?
(ii) How many unit cells are there in 1.00 cm
Solution:
Given r = 125 p m , a = ? , = c c p ( f c c )
( i ) For ccp ( f c c ) , a = 2 √ 2 r
= 2 × 1.414 × 125 p m = 354 p m
= 2 × 1.414 × 125 p m = 354 p m ( i i )
Volume of one unit cell = a 3
= ( 354 × 10 − 10 c m ) 3 = 4.44 × 10 − 23 c m 3
Number of unit cells in1 c m 3 =
= 2.25 × 10 22
Number of unit cells in
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