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The density of KBr is "2.75 g/cm"^3 and ...

The density of KBr is `"2.75 g/cm"^3` and edge length of unit cell is 654 pm (K=39 , Br=80) then what are the features of this unit cell ?

A

Unit cell is fcc

B

Z = 4

C

There are four constituents/unit cells

D

There are 8 ions at corners and 6 at the centres of the faces

Text Solution

Verified by Experts

The correct Answer is:
A,B,C,D
`z=(rho xx a^(3)xx10^(-30)xx N_(0))`
`=(2.75xx(654)^(3)xx10^(-30)xx6.02xx10^(23))/(119)=4`
As Z = 4, it is fcc unit cell. There are four KBr units. There are 8 ions at the comers and 6 at the face centres.
Hence (A), (B), (C ) and (D) are the the correct answers.
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