An element crystallises in bcc lattice with a cell edge of 3 × 10⁻⁸ cm. The density of the element is 6.89 g cm⁻³. Calculate the molar mass of the element. (Nₐ = 6.022 × 10²³ mol⁻¹)

Formula units per unit cell for BCC (Z) = 2
Edge of lattice (a) = 3 × 10⁻⁸ cm
Density of element (d) = 6.89 g/cm³
Nₐ = 6.022 × 10²³
Molar mass of element (M) = ?
As we know that,
M = d × Nₐ × a³ / Z
⇒ M = 6.89 × 6.022 × 10²³ × (3 × 10⁻⁸)³ / 2
≈ 56 g
Hence the molar mass of the element is 56 g.