:3

Đáp án:

\({{\text{C}}_{M{\text{ NaOH}}}} = 1M\)

Giải thích các bước giải:

 Phản ứng xảy ra:

\(N{a_2}O + {H_2}O\xrightarrow{{}}2NaOH\)

Ta có: 

\({n_{N{a_2}O}} = \frac{{15,5}}{{23.2 + 16}} = 0,25{\text{ mol}} \to {{\text{n}}_{NaOH}} = 2{n_{N{a_2}O}} = 0,5{\text{ mol}} \to {{\text{C}}_{M{\text{ NaOH}}}} = \frac{{0,5}}{{0,5}} = 1M\)

Phản ứng trung hòa:

\(2NaOH + {H_2}S{O_4}\xrightarrow{{}}N{a_2}S{O_4} + 2{H_2}O\)

\( \to {n_{{H_2}S{O_4}}} = \frac{1}{2}{n_{NaOH}} = 0,25{\text{ mol}} \to {{\text{m}}_{{H_2}S{O_4}}} = 0,25.98 = 24,5{\text{ gam}} \to {{\text{m}}_{dd{\text{ }}{{\text{H}}_2}S{O_4}}} = \frac{{24,5}}{{20\% }} = 122,5{\text{ gam}} \to {{\text{V}}_{dd{\text{ }}{{\text{H}}_2}S{O_4}}} = \frac{{122,5}}{{1,14}} = 107,456{\text{ ml}}\)

Dung dịch sau phản ứng chứa 

\({n_{N{a_2}S{O_4}}} = {n_{{H_2}S{O_4}}} = 0,25{\text{ mol; }}{{\text{V}}_{dd}} = {V_{dd{\text{NaOH}}}} + {V_{dd\;{{\text{H}}_2}S{O_4}}} = 0,5 + 0,107456 = 0,607456 \to {C_{M{\text{ N}}{{\text{a}}_2}S{O_4}}} = \frac{{0,25}}{{0,0607456}} = 0,4155M\)