Question

If some moles of $O_2$ diffuse in 18 sec and same moles of other gas diffuse in 45 sec then what is the molecular weight of the unknown gas

• A. $\frac{{45}^2}{{18}^2}\times 32$
• B. $\frac{{18}^2}{{45}^2}\times 32$
• C. $\frac{{18}^2}{{45}^2\times 32}$
• D. $\frac{{45}^2}{{18}^2\times 32}$

Answer 1

The correct option is A

$\frac{{45}^2}{{18}^2}\times 32$

$r_{O_2}=\frac{x}{18}mole/sec\Rightarrow r_8=\frac{x}{45}mol/sec$

$M_g=M_{O_2}(\frac{r_{O_2}}{r_g}{)}^2=32(\frac{x}{18}\times \frac{45}{x}{)}^2=32\times \frac{{45}^2}{{18}^2}$