A neon-dioxygen mixture contains  $70.6{\mathrm{gO}}_2\text{ and }167.5\mathrm{g}$neon. If pressure of the mixture of gases in the cylinder is 25 bar. What is the partial pressure of O₂, and Ne in the mixture respectively? 

$$\begin{gathered} \text{ Number of moles of }{\mathrm{O}}_2=\frac{70.6\mathrm{g}}{32\mathrm{g}{\mathrm{mol}}^{-1}}=2.21\mathrm{mol} \\ \text{ Number of moles of }\mathrm{Ne}=\frac{167.5\mathrm{g}}{20\mathrm{g}{\mathrm{mol}}^{-1}}=8.375\mathrm{mol} \\ \text{ Mole fraction of }{\mathrm{O}}_2=\frac{2.21}{2.21+8.375}=0.21 \\ \text{ Mole fraction of }\mathrm{Ne}=1-0.21=0.79 \end{gathered}$$
Partial pressure of a gas = Mole fraction x total pressure
$$\begin{gathered} \text{ Partial pressure of }{\mathrm{O}}_2=0.21\times 25=5.25\mathrm{bar} \\ \text{ Partial pressure of }\mathrm{Ne}=0.79\times 25=19.75\mathrm{bar} \end{gathered}$$