a, \(C_2H_2+2Br_2\rightarrow C_2H_2Br_4\)
\(n_{Br_2}=\dfrac{8}{160}=0,05\left(mol\right)\)
\(n_{C_2H_2}=\dfrac{1}{2}n_{Br_2}=0,025\left(mol\right)\Rightarrow m_{C_2H_2}=0,025.26=0,65\left(g\right)\)
b, \(\left\{{}\begin{matrix}\%V_{C_2H_2}=\dfrac{0,025.22,4}{33,6}.100\%\approx1,67\%\\\%V_{CH_4}\approx98,33\%\end{matrix}\right.\)