The sublimation temperature of a substance is -83 °C. It exist as cubic packed structure with unit cell edge length 5.0 Å and density 8/3 g/cm³, at -100 °C. What should be density of substance at 0 °C

Question

The sublimation temperature of a substance is -83 °C. It exist as cubic packed structure with unit cell edge length 5.0 Å and density 8/3 g/cm³, at -100 °C. What should be density of substance at 0 °C and 1 atm? (Na = 6 × 10^23)

Prashant Kotian · Accepted Answer

Correct answer: C. Since the sublimation temperature is -83 °C, the substance exists in the gaseous state at 0 °C and 1 atm (above -83 °C). First, find the molar mass M from solid state at -100 °C: ρ = (Z × M) / (Na × a³) => 8/3 = (4 × M) / (6 × 10^23 × (5 × 10^-8)³) => M = 50 g/mol. At 0 °C and 1 atm (ideal gas at STP), density ρ_gas = M / 22.4 L = 50 / 22.4 ≈ 2.23 g/l.

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