\(n_{CO} = a ; n_{H_2} = b ; M_A = 5,375.4 = 21,5(g/mol)\\ m_A = n_A.M_A\\ \Leftrightarrow 28a + 2b = (a + b)21,5\\ \Leftrightarrow 6,5a = 19,5b\\ \Leftrightarrow \dfrac{a}{b} = \dfrac{19,5}{6,5} = \dfrac{3}{1}\\ \%V_{CO} = \dfrac{3}{3+1} .100\% = 75\%\\ \%V_{H_2} = \dfrac{1}{3+1}.100\% = 25\%\)