Question

A certain gas takes three times as long to effuse out as helium. Its molecular mass will be:

• A. 36 u
• B. 64 u
• C. 9 u
• D. 27 u

Answer 1

The Correct Option is A

$\frac{r_{1}}{r_{2}} = \sqrt{\frac{M_{w_2}}{M_{w_1}}} $
$ \frac{V_{1}}{t_{1}} \times\frac{t_{2}}{V_{2}} = \sqrt{\frac{M_{W_2}}{M_{W_1}}} $
volume is same
$ \frac{3}{1} = \sqrt{\frac{M_{W_2}}{4}} $
$ 9 = \frac{M_{W_2}}{4} \therefore M_{W_2} = 36 $

Answer 2

Since the volume is the same, the specific gas that will take three times longer to evaporate than helium has a molecular mass of 36 u, and \(\frac{3}{1}\) equals the root square of \(\frac{Mw_2}{4}\).
The mass, calculated, is 36 u.