Question

One mole of nitrogen gas at 0,8 atm takes 38 seconds to diffuse through a pinhole whereas one mole of an unknown compound of xenon with fluorine at 1.6 atm takes 56.26 seconds to diffuse through the same hole, then the molecular formula of the compound is: (Atomic mass of Xenon: 131.3 u)

• A. ${XeF}_2$
• B. ${XeF}_4$
• C. ${XeF}_5$
• D. ${XeF}_6$

Answer 1

Answer: (D)

${XeF}_6$

rate of diffusion $\alpha \frac{PA}{\sqrt{MT}}$

$\therefore \frac{T_1}{T_2}=\frac{\sqrt{T_1{M}_1}}{\sqrt{T_2{M}_2}}\frac{P_2{A}_2}{P_1{A}_1}\Rightarrow \frac{98}{56.26}=\frac{\sqrt{28}}{\sqrt{M_2}}\times \frac{1.6}{0.8}$

$\Rightarrow \frac{\sqrt{M_2}}{\sqrt{28}}=\frac{56.26}{19}$

$\Rightarrow M_2=\frac{28\times 56.26\times 56.26}{19\times 19}=245.5$

$\therefore$ Mass of $F$ in compound $=245.5-131.3$

$=114\Rightarrow 19x.11$

$X_e{F}_6$ molecular formula