$n_{CH_3CH_2OH}=2a mol$
$CH_3CH_2OH+2[O]\rightarrow CH_3COOH+H_2O$ $2x 2x 2x$
$\Rightarrow \begin{cases}\frac{n_{CH_3CH_2OH du}+n_{CH_3COOH}+n_{H_2O}}{2.2}=\frac{6,272}{22,4} \\ \frac{n_{CH_3COOH}}{2}=\frac{2.120}{1000} \end{cases}$
$\Rightarrow \begin{cases}\frac{(2a-2x)+2x+2x}{4}=0,28 \\ \frac{2x}{2}=0,24 \end{cases}\Rightarrow \begin{cases}x=0,24 mol \\ a=0,32 mol \end{cases}\Rightarrow H=\frac{2x}{2a}.100=75\%$