Estimate the density of magnesium oxide from its crystal structure.The radii of Mg²⁺ and O²^- are 72 and 140 pm,respectively. A)3.51 g.cm^-3 B)14.9 g.cm^-3 C)21.1 g.cm^-3 D)1.76 g.cm^-3 E)0.878 g.cm^-3

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Quizplus · Accepted Answer

Magnesium oxide has a rock salt structure. The volume of the unit cell is (2r_Mg²⁺ + 2r_O^2-)³ = (2 * 72 pm + 2 * 140 pm)³ = 1.69 * 10^-23 cm³The mass of the unit cell is (1 * 24.31 g/mol + 1 * 16.00 g/mol) * (1/6.022 * 10²³ mol^-1) = 6.65 * 10^-23 gTherefore, the density is (6.65 * 10^-23 g) / (1.69 * 10^-23 cm³) = 3.94 g/cm³

Estimate the Density of Magnesium Oxide from Its Crystal Structure