NEET Chemistry The Solid State Questions Solved


A metal crystallizes in two cubic phases, face centred cubic (fcc) and body centred cubic (bcc) whose unit cell length are 3.5 and 3.0 Å respectively. Calculate the ratio of density of fcc and bcc. 

(A) 2.123                                     

 (B) 1.259

(C) 5.124                                       

(D) 3.134

(B). ρ=n×MmNA×a3

For fcc centred cubic cell n = 4, a = 3.5 Å

  ρfcc=4×MmNA×3.53                                                   ........(i)    

For bcc lattice
n = 2, a = 3.0 Å

ρbcc=2×mmNA×3.03                                                       ........(ii)

From equations (i) and (ii)

 ρfccρbcc=42×333.53=4×3×3×32×3.5×3.5×3.5=1.259

Difficulty Level:

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