Câu hỏi 30

Giả sử chất béo là \({(\overline R C{\text{OO)}}_{\text{3}}}{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{5}}}\)

\(\begin{gathered}
{(\overline R C{\text{OO)}}_{\text{3}}}{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{5}}}\xrightarrow{{ + KOH}}3\overline R C{\text{OO}}K \hfill \\
{(\overline R C{\text{OO)}}_{\text{3}}}{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{5}}}\xrightarrow{{ + NaOH}}3\overline R C{\text{OONa}} \hfill \\
\,\,\,\,\,\,\,\,\overline R C{\text{OO}}K..............\overline R C{\text{OONa}} \hfill \\
PT:\overline R + 83..................\overline R + 67 \hfill \\
DB:18,77g................17,81g \hfill \\
\to 18,77(\overline R + 67) = 17,81(\overline R + 83) \hfill \\
\to \overline R = \frac{{1379}}{6} \hfill \\
n\overline R C{\text{OO}}K = \frac{{18,77}}{{\frac{{1379}}{6} + 83}} = 0,06(mol) \hfill \\
\to n{(\overline R C{\text{OO)}}_{\text{3}}}{{\text{C}}_{\text{3}}}{{\text{H}}_{\text{5}}} = 0,02mol \hfill \\
\to m = 0,02\left[ {(\frac{{1379}}{6} + 44).3 + 41} \right] = 17,25(g) \hfill \\
\end{gathered} \)

Đáp án B