An unknown gas is discovered to effuse at a rate that is 1.85 times faster than Radon. What is the molar mass of the gas?

1 Answer
Junaid Mirza
May 10, 2018

#"64.9 g/mol"#

Explanation:

From Graham's law of effusion

#"r" ∝ 1/sqrt("M")#

#"r"_"Ra"/"r"_"gas" = sqrt("M"_"gas"/"M"_"Ra")#

On rearranging,

#"M"_"gas" = "M"_"Ra" × ["r"_"Ra"/"r"_"gas"]^2#

#"M"_"gas" = "222 g/mol" × [(cancel("r"_"Ra"))/(1.85 × cancel("r"_"Ra"))]^2 ≈ "64.9 g/mol"#

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