G/sử `n_{A}=1(mol)`
Đặt $\begin{cases} n_{H_2}=x(mol)\\n_{O_2}=y(mol) \end{cases}$ `->x+y=1` $(1)$
$\overline{M_{A}}$ `=8,5.2=17` $(g/mol)$
`=>(2x+32y)/(1)=17`
`=>2x+32y=17` $(2)$
$(1)(2)$ `->` $\begin{cases} x=0,5(mol)\\y=0,5(mol)\end{cases}$
`%V_{H_2}=%V_{O_2}=(0,5)/(0,5+0,5).100%=50%`
`%m_(H_2` `=(0,5.2)/(0,5.(2+32)).100%≈5,88%`
`%m_{O_2}=100-5,88=94,12%`