Question

An element (atomic mass M g/mol) having bcc structure has unit cell edge 400 pm. The density of the element is ____________ g/cm³.

[N_A = 6.0 × 10²³ atom mol⁻¹)

Options

• `"M"/6.4`

• `"M"/19.2`

• `"M"/9.6`

• `"M"/38.4`

Answer 1

An element (atomic mass M g/mol) having bcc structure has unit cell edge 400 pm. The density of the element is `underline("M"/19.2)` g/cm³.

Explanation:

For bcc unit cell, n = 2

400 pm = 400 × 10⁻¹⁰ cm

ρ = `("n M")/("a"^3 "N"_"A")`

= `(2 xx "M")/((400)^3 xx 10^-30 xx (6.0 xx 10^23))`

= `"M"/19.2` g/cm³