Đáp án:
3,988 g
Giải thích các bước giải:
\(\begin{array}{l}
{M_{hhA}} = \dfrac{2}{3} \times {M_{N{O_2}}} = \dfrac{2}{3} \times 46 = \dfrac{{92}}{3}\,g/mol\\
{n_{hh\,A}} = \dfrac{4}{{\dfrac{{92}}{3}}} = \dfrac{3}{{23}}\,mol\\
hh\,A:{H_2}(a\,mol),{O_2}(b\,mol)\\
\left\{ \begin{array}{l}
a + b = \dfrac{3}{{23}}\\
2a + 32b = 4
\end{array} \right.\\
\Rightarrow a = \dfrac{2}{{345}};b = \dfrac{{43}}{{345}}\\
{m_{{O_2}}} = \dfrac{{43}}{{345}} \times 32 \approx 3,988g
\end{array}\)