$\begin{cases}n_{H_2}=x mol \\n_{C_nH_{2n}}=y mol \end{cases}$$C_nH_{2n}+H_2\rightarrow C_nH_{2n+2}$
$y y y$
$\Rightarrow \begin{cases}\frac{2x+14ny}{x+y}=2.6 \\ \frac{2(x-y)+(14n+2)y}{(x-y)+y}=2.11,8 \end{cases}\Rightarrow \frac{x}{x+y}=\frac{6}{11,8}\Rightarrow x=\frac{6y}{5,8}$
$\Rightarrow \frac{\frac{6y}{5,8}+7ny}{\frac{6y}{5,8}+y}=6\Rightarrow \frac{6+40,6n}{11,8}=6\Rightarrow n=1,59.....????$