UPSEE Solved Model Paper 1

The number of oxygen atoms per unit cell in CCP = 4(O−2)
The number of octahedral voids per unit cell = 4(Al+3)
The number of tetrahedral voids per unit cell = 8(Mg+2)
Overall magnitude of negative charge due to oxygen atoms = 8
Overall, the unit cell isneutral, hence:
m4(3) + 2n(8)+ 4(-2) = 0
3m + 4n = 2
In the above equation, substitute the values of the given options.
(A)

3

4

+

4

8

= 2 is right. The others don't work out.