\(a) C_2H_2 + 2Br_2 \to C_2H_2Br_4\\ b) m_{tăng} = m_{C_2H_2} = 5,2(gam)\\ \Rightarrow n_{C_2H_2} = \dfrac{5,2}{26} = 0,2(mol)\\ \Rightarrow n_{CH_4} = \dfrac{8,96}{22,4} - 0,2 = 0,2(mol)\\ \Rightarrow V_{C_2H_2} = V_{CH_4} =0,2.22,4 = 4,48(lít)\\ \%V_{C_2H_2} = \%V_{CH_4} = \dfrac{4,48}{8,96}.100\% = 50\%\\ \)