Question

A compound AB has a simple cubic structure and has a molecular mass of 99. Its density is 3.4 g cm⁻³. What will be the edge length of the unit cell?

Answer 1

Given: M = 99

Z = 1 (sc)

ρ = 3.4 g/cm³

N_A = 6.022 × 10²³

To find: a = ?

Formula: `rho = (Z xx M)/(N_A xx a^3)`

`a^3 = (Z xx M)/(N_A xx rho)`

= `(1 xx 99)/(6.022 xx 10^23 xx 3.4)`

= `(99)/(20.4748 xx 10^23)`

= 4.835 × 10⁻²³ cm³

= `(4.835 × 10^(−23))^(1/3)`

= 3.64 × 10⁻⁸ cm

= 364 pm

= 3.64 Å