Question

A compound AB has a rock salt type structure with A:B=1:1 . The formula weight of AB is 6.023 y amu and the closest A-B distance is `y^(1//3)` nm. Calculate the density of lattice (in `kg//m^(3))`

Answer 1

Correct Answer - 5
AB has rock slat (A:B::1:1) structure, i.e, f.c.c. structure (n=4) and formula weight of BB is 6.023 y amu having closet distance `A-B_(Y^(1//3))`nm. Therefore edge length of unit cell `=2(A^(+)+B^(-))=2xxy^(1//3)xx10^(-9)m`
`therefore "Density of AB"(nxx"mol wt.")/(Av. no. xxV)`
`=(4xx6.023xxyxx10^(-3))/(6.023xx10^(23)xx(2y^(1//3)xx10^(-9))^(3))` (mol. wt. in kg)
=5.0kg `m^(-3)`