Đáp án:
\( \m = 131,4815{\text{ gam}}\)
Giải thích các bước giải:
Phản ứng xảy ra:
\(3{H_2}O + {P_2}{O_5}\xrightarrow{{}}2{H_3}P{O_4}\)
Ta có:
\({m_{dd}} = {m_{{P_2}{O_5}}} + {m_{dd{\text{ }}{{\text{H}}_3}P{O_4}}} = m + 200{\text{ gam}}\)
\({m_{{H_3}P{O_4}{\text{ ban đầu}}}} = 200.39,2\% = 78,4{\text{ gam}}\)
\({n_{{P_2}{O_5}}} = \frac{m}{{31.2 + 16.5}} = \frac{m}{{142}}{\text{ mol}} \to {{\text{n}}_{{H_3}P{O_4}}} = 2{n_{{P_2}{O_5}}} = \frac{m}{{71}}{\text{ mol}}\)
\( \to {m_{{H_3}P{O_4}}} = 78,4 + \frac{m}{{71}}.98 = (200 + m).78,4\% \)
\( \to m = 131,4815{\text{ gam}}\)
