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

  • Option 1)

    36 u

  • Option 2)

    64 u

  • Option 3)

    9 u

  • Option 4)

    27 u

 

Answers (1)

As we lernt in

Graham’s law of diffusion -

\dpi{100} r_{1}/r_{2}=\sqrt{M_{1}/M_{2}}  where r is rate of diffusion of gas , M is molar mass.

-

 

 

As per graham's law of diffusion

 

\frac{r_{1}}{r_{2}}=\sqrt{\frac{M_{2}}{M_{1}}}

given that \frac{r_{1}}{r_{2}}={\frac{1}{3}}

M_{2}=4

\Rightarrow \frac{1}{3}=\sqrt{\frac{4}{M_{1}}}

\Rightarrow \frac{1}{9}={\frac{4}{M_{1}}}

\Rightarrow M_{1}=4\times 9 = 36


Option 1)

36 u

This is correct answer

Option 2)

64 u

This is incorrect answer

Option 3)

9 u

This is incorrect answer

Option 4)

27 u

This is incorrect answer

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