\(n_{CO_2}=\dfrac{V_{CO_2}}{22.4}=\dfrac{0.672}{22.4}=0.03mol\\ \Rightarrow n_C=0.03mol\\ \Rightarrow m_C=0.03\times12=0.36g\\ \Rightarrow\%C=\dfrac{m_C}{m_{hidrocacbon}}\times100\%=\dfrac{0.36}{0.44}\times100\%=81.82\%\\ \Rightarrow\%H=100\%-\%C=18.18\%\)