Đáp án:

\(C\%  = 30,03\% \)

Giải thích các bước giải:

\(\begin{array}{l}
2Na + {H_2}S{O_4} \to N{a_2}S{O_4} + {H_2}\\
Mg + {H_2}S{O_4} \to MgS{O_4} + {H_2}\\
Na + {H_2}O \to NaOH + \dfrac{1}{2}{H_2}
\end{array}\)

Giả sử lấy 100g dung dịch \({H_2}S{O_4}\)

\(\begin{array}{l}
{n_{{H_2}S{O_4}}} = \dfrac{{100 \times C\% }}{{100\%  \times 98}} = \dfrac{C}{{98}}mol\\
{m_{{H_2}O}} = 100 - C(g)\\
 \to {n_{{H_2}O}} = \dfrac{{100 - C}}{{18}}mol\\
 \to {n_{{H_2}}} = {n_{{H_2}S{O_4}}} + \dfrac{1}{2}{n_{{H_2}O}} = \dfrac{C}{{98}} + \dfrac{{100 - C}}{{36}}mol\\
 \to {m_{{H_2}}} = (\dfrac{C}{{98}} + \dfrac{{100 - C}}{{36}}) \times 2 = 100 \times 4,5\% \\
 \to C = 30,03\% 
\end{array}\)