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The cubic unit cell of Al (molar mass 27...

The cubic unit cell of Al (molar mass 27 g `mol^(-1)`) has an edge length of 405 pm. Its density is 2.7g `cm^(-3)`. The cubic unit cell is

A

a) face centred

B

b) body centred

C

c) primitive

D

d) edge centred

Text Solution

Verified by Experts

The correct Answer is:
A
Density `(rho)=(ZxxM)/(a^(3)xxN_(0))`
`27=(Zxx27)/((405xx10^(-10))^(3)xx6.023xx10^(23))`
`Z=(27xx(405)^(3)xx10^(-30)xx6.023xx10^(23))/(27)`
`=4`
For face centred cubic unit cell, number of atoms are 4.
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