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The root mean square speed of an unknown gas at 727 deg C is 10⁵ cm/s. Calculate the molar mass of the gas in g/mol. (Given: R = 25/3 J/(mol K))

1. 25
2. 50
3. 75
4. 100

Correct answer: 25

Solution

Substituting v_rms = 1000 m/s and T = 1000 K into v_rms² = 3RT/M gives M = 3*(25/3)*1000/10⁶ = 0.025 kg/mol = 25 g/mol.

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