Question

What is the edge length of fcc type of unit cell having density and atomic mass 6.22 g cm⁻³ and 60 g respectively?

Options

• 6.83 × 10⁻⁷ cm

• 4.0 × 10⁻⁸ cm

• 3.47 × 10⁻⁷ cm

• 8.0 × 10⁻⁸ cm

Answer 1

4.0 × 10⁻⁸ cm

Explanation:

Density = `("n" xx "M")/("a"^2 xx "N"_0)`

6.22 = `(4 xx 60)/("a"^3 xx 6.023 xx 10^23)`

a³ = `(240)/(6.22 xx 6.023 xx 10^23)`

= `2400/(6.22 xx 6.023 xx 10^24)`

a³ = 64.06 × 10⁻²⁴ 

a = 4 × 10⁻⁸ cm