Question

A metallic element has a cubic lattice with edge length of unit cell 2 Å. Calculate the number of unit cells in 200 g of the metal, if density of metal is 2.5 g cm^-3?

Options

• 10.0 × 10²⁵

• 6.25 × 10²⁵

• 6.40 × 10²⁵

• 1.0 × 10²⁵

Answer 1

1.0 × 10²⁵ 

Explanation:

Number of unit cells in 200 g of the metal = `200/(2.5 (2 xx 10^-8 "cm")^3)`

`= 200/(2.5 xx 8 xx 10^-24) = 200/20`

= 1.0 × 10²⁵