[Single-digit Integer] Iron(II) oxide crystal has a cubic structure and each edge of the unit cell is 0.493 nm. If the density of the oxide is 4.0 g/cm3, the number of iron (II) oxide formula units in

Question

[Single-digit Integer] Iron(II) oxide crystal has a cubic structure and each edge of the unit cell is 0.493 nm. If the density of the oxide is 4.0 g/cm3, the number of iron (II) oxide formula units in each unit cell is (Fe = 56)

Prashant Kotian · Accepted Answer

Correct answer: 4. Molar mass of = 56 + 16 = 72 g/mol. Volume of unit cell V = a^3 = (0.493 * 10^-7 cm)^3 = 1.198 * 10^-22 cm3. Density ρ = (Z * M) / (Na * V) => 4.0 = (Z * 72) / (6.022 * 10^23 * 1.198 * 10^-22) = (Z * 72) / 72.14 => Z = 4 formula units per unit cell.

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