Chemistry - Concentration Terms Question with Solution | TestHub

Gaseous benzene reacts with hydrogen gas in presence of a nickel catalyst to form gaseous cyclohexane according to the reaction, ${\mathrm{C}}_6{\mathrm{H}}_6(g)+3{\mathrm{H}}_2(g)⟶{\mathrm{C}}_6{\mathrm{H}}_{12}(g)$ A mixture of ${\mathrm{C}}_6{\mathrm{H}}_6$ and excess ${\mathrm{H}}_2$ has a pressure of $60\mathrm{mm}$ of $\mathrm{Hg}$ in an unknown volume. After the gas had been passed over a nickel catalyst and all the benzene converted to cyclohexane, the pressure of the gas was $30\mathrm{mm}$ of $\mathrm{Hg}$ in the same volume at the same temperature. The fraction of ${\mathrm{C}}_6{\mathrm{H}}_6$ (by volume) present in the original volume is