NCERT Class XII Chemistry <br> Chapter - The Solid State <br> Questions with Solutions

NCERT Class XII Chemistry
Chapter - The Solid State
Questions with Solutions

Question : 13

Total: 50

13.Niobium crystallises in body-centred cubic structure. If density is 8.55 g cm‌–3, calculate atomic radius of niobium using its atomic mass 93 u.

Solution:

Given d=8.55g cm−3,M=93 g mol−1,Z=2 (for bcc) ,NA=6.022×1023,r=?
Using formula
a3=

M×Z

d×NA

93×2

8.55×6.022×1023

⇒a3=3.61×10−23
‌‌‌‌‌‌‌=36.1×10−24
∴‌‌‌a=3.304×10−8 cm
‌‌‌‌‌‌‌‌=330.4×10−12m
‌‌‌‌‌‌‌‌=330.4 pm
For body-centred cubic,
r=

√3

a
=0.433a
=0.433×330.4 pm
=143.1pm

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