Pure $O_{2}$ diffuses through an aperture in 224 s, whereas a mixture of $O_{2}$ and another gas containing 80% $O_{2}$ diffuses from the same in 234 s under similar conditions of pressure and temperature. What is molecular weight of gas?

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Pure O2 diffuses through an aperture in 224 sec, whereas a mixture of O2 and another gas containing 80% O2 diffuses from the same in 234 sec. What is the molecular weight of the gas?[as nearest integer]

t2t1=√MmixM234224=√Mmix32⇒Mmix=34.92=1008032+20MM=46.6≈47

Pure $O_{2}$ diffuses through an aperture in 224 sec, whereas a mixture of $O_{2}$ and another gas containing 80% $O_{2}$ diffuses from the same in 234 sec. What is the molecular weight of the gas?
[as nearest integer]

$\frac{t_{2}}{t_{1}} = \sqrt{\frac{M_{m i x}}{M}}$

$\frac{234}{224} = \sqrt{\frac{M_{m i x}}{32}}$

$\Rightarrow M_{m i x} = 34.92 = \frac{100}{\frac{80}{32} + \frac{20}{M}}$
$M = 46.6 \approx 47$