Em tham khảo nha :
\(\begin{array}{l}
a)\\
{M_A} = 8{M_{{H_2}}} = 16dvC\\
hh:{H_2}(a\,mol),{O_2}(b\,mol)\\
\dfrac{{2a + 32b}}{{a + b}} = 16\\
\Rightarrow 2a + 32b = 16a + 16b\\
\Rightarrow \dfrac{a}{b} = \dfrac{{32 - 16}}{{16 - 2}} = \frac{8}{7}\\
\% {V_{{H_2}}} = \dfrac{8}{{7 + 8}} \times 100\% = 53,33\% \\
\% {V_{{O_2}}} = 100 - 53,33 = 46,67\% \\
\% {m_{{H_2}}} = \dfrac{{8 \times 2}}{{8 \times 2 + 32 \times 7}} \times 100\% = 6,67\% \\
\% {m_{{O_2}}} = 100 - 6,67 = 93,33\% \\
b)\\
2{H_2} + {O_2} \to {H_2}O\\
\dfrac{{{n_{{H_2}}}}}{2} < \dfrac{{{n_{{O_2}}}}}{1} \Rightarrow {O_2}\text{ dư}\\
{n_{{H_2}O}} = {n_{{H_2}}} = a\,mol\\
{m_{{H_2}O}} = n \times M = 18a\,g
\end{array}\)