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Grade 12Physical Chemistry

A metal crystallises in two phases, fcc and bcc, whose unit cell lengths are 3.5 Armstrog and 3.0 Armstrong respectively. The ratio of density of fcc and bcc is?

Profile image of Sai Soumya
8 Years agoGrade 12
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3 Answers

Profile image of Adarsh
ApprovedApproved Tutor Answer8 Years ago
Dear Sai,
the answer will be 1.259 .  Use the formula for density, = z.M/Na.a3. .
Thanks and Regards
Adarsh
Profile image of Khimraj
ApprovedApproved Tutor Answer8 Years ago
Density is given by
d = (z*M)/(a3*NA)
given that a1 = 3.5 A0 and a2 = 3.0 A0
No of atom per unit cell of fcc z1 = 4
No of atom per unit cell of fcc z2 = 2
Sonratio of density of fcc and bcc
d1/d2 = (z1/z2)*(a2/a1)3 = (4/2)*(3/3.5)3 = 2*(6/7)3 =432/343.
Hope it clears. If you like answerthen please approve it.
Profile image of Anjali kumari
8 Years ago
As density= Z..M/Na.a^3. You will get 432:343.If you like the answer please approve it.Thank you. Gusto do TCP go gdp cpc