# A mixture of 2 moles of helium gas, and 1 mole of argon gas is kept at 300 K in a container.

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A mixture of 2 moles of helium gas (atomic mass = 4 u), and 1 mole of argon gas (atomic mass = 40 u) is kept at 300 K in a container. The ratio of their rms speeds $\left[{V_{rms}(helium)\over V_{rms}(argon)}\right]$, is close to :

(1) 2.24

(2) 0.45

(3) 0.32

(4) 3.16

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Ans: (4) 3.16

Sol:  ${V_{rms}(He)\over V_{rms}(Ar)}=\sqrt{M_{Ar}\over M_{He}}=\sqrt{40\over4}=3.16$