A quantity of 5.0 g of a mixture of He and another gas occupies a volume of 1.5 l at 300 K and 750 mm Hg. The gas freezes at 270 K. At 15 K, the pressure of the gas mixture is 8 mm Hg (at the same vol

Question

A quantity of 5.0 g of a mixture of He and another gas occupies a volume of 1.5 l at 300 K and 750 mm Hg. The gas freezes at 270 K. At 15 K, the pressure of the gas mixture is 8 mm Hg (at the same volume). What is the molecular mass of the gas?

Prashant Kotian · Accepted Answer

Correct answer: A. at 15 k, the other gas is frozen, so pressure is due only to he. p_he at 15 k = 8 mm hg. at 300 k, p_he = 8 × (300/15) = 160 mm hg. p_other at 300 k = 750 - 160 = 590 mm hg. n_he = (160/760) × 1.5 / (0.0821 × 300) = 0.0128 mol. mass of he = 0.051 g. mass of other gas = 5.0 - 0.051 = 4.949 g. moles of other gas = (590/760) × 1.5 / (0.0821 × 300) = 0.0473 mol. molecular mass of other gas = 4.949 / 0.0473 = 104.6 g/mol ≈ 103.8.

💡 Solution & Explanation

Practice 22,000+ questions like this