Chemistry - Mole Concept Question with Solution | TestHub

${\mathrm{C}}_6{\mathrm{H}}_6\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to {\mathrm{C}}_6{\mathrm{H}}_{12}\left(\mathrm{g}\right)$

Let x and y be the partial pressures (initial) of gaseous benzene and hydrogen in the vessel.

Then,$\text{x}+\text{y}=60$......... (i)

After the reaction, whole of benzene is converted to cyclohexane.

Partial pressure of cyclohexane$= x\; mmHg$

Partial pressure of hydrogen left unreacted$=\text{y}-3\text{x}$

Total pressure of the system after the reaction,

$\text{x}+\text{y}-3\text{x}=\text{y}-2\text{x}=30$.......... (ii)

Solving (i) and (ii),$\text{x}=10\; mmHg$

Number of moles$\propto$pressure ; Volume$\propto$number of moles

Hence, fraction of benzene by volume in the original mixture$=\frac{10}{60}=\frac{1}{6}=\text{0.167}$