The general equation for burning of hydrocarbon is given as ${\mathrm{C}}_{\mathrm{x}}{\mathrm{H}}_{\mathrm{y}}$.

${\mathrm{C}}_{\mathrm{x}}{\mathrm{H}}_{\mathrm{y}}+\underset{\mathrm{excess}}{{\mathrm{O}}_2}\to {\mathrm{xCO}}_2+\frac{\mathrm{y}}{2}{\mathrm{H}}_2\mathrm{O}$.

According to Avogadro's hypothesis, gases react with each other in the same proportion of volume as moles. From this, we can write the equation as:

$$\begin{gathered} 10{\mathrm{C}}_{\mathrm{x}}{\mathrm{H}}_{\mathrm{y}}+\underset{\mathrm{excess}}{{\mathrm{O}}_2}\to 40{\mathrm{CO}}_2+50{\mathrm{H}}_2\mathrm{O} \\ 1{\mathrm{C}}_{\mathrm{x}}{\mathrm{H}}_{\mathrm{y}}+\underset{\mathrm{excess}}{{\mathrm{O}}_2}\to 4{\mathrm{CO}}_2+5{\mathrm{H}}_2\mathrm{O}. \end{gathered}$$

Comparing with the general equation, we get:

$\mathrm{x}=4$ and $\frac{\mathrm{y}}{2}=5$.

So, $\mathrm{y}=10$.

Hence, the hydrocarbon is ${\mathrm{C}}_4{\mathrm{H}}_{10}$.