
Mole of $H _2$ gas
$\Rightarrow 1 \times \frac{8.40}{1000}= n \times 0.0821 \times 273$
$\Rightarrow n =3.75 \times 10^{-4}$
Hydrogen molecule used for 1 molecule of hydrocarbon is 3
$=\frac{3.75 \times 10^{-4}}{1.25 \times 10^{-4}}=3$
$C{H_3}C \equiv \,C\,C{H_2}C{H_3}\mathop {\xrightarrow[{(2)\;Hydrolysis}]{}}\limits^{(1)\;\;{O_3}} $ .......