Đốt cháy hoàn toàn m gam hỗn hợp X

Chọn đáp án B

Ta thấy chất béo tạo từ 3 gốc axit $\left\{\begin{array}{l}{C}_{17}{H}_{33}COOH\\ C_{17}{H}_{31}COOH\\ C_{15}{H}_{31}COOH\end{array}\right.\stackrel{CTPTchung}{\to }k=6〈\begin{array}{l}3lk\pi trong-COO-\\ 1lk\pi trong-C_{17}{H}_{33}-\\ 2lk\pi trong-C_{17}{H}_{31}-\end{array}$

Dùng CT liên hệ:$\boxed{n_{C{O}_2}+n_{N_2}-n_{H_{2}O}=(k-1).n_X}$

$\Rightarrow \underset{\mathrm{0,55}}{\underbrace{n_{C{O}_2}}}-\underset{\mathrm{0,5}}{\underbrace{n_{H_{2}O}}}=(\underset{6}{\underbrace{k}}-1).n_X\iff n_X=\mathrm{0,01}\Rightarrow n_O=6\underset{\mathrm{0,01}}{\underbrace{n_X}}\Rightarrow n_O=\mathrm{0,06}$

BTKL trong X: $m_X=\underset{\stackrel{BTNTC}{\to }\mathrm{0,55.12}}{\underbrace{m_C}}+\underset{\stackrel{BTNTH}{\to }\mathrm{0,5.2}}{\underbrace{m_H}}+\underset{\mathrm{0,06.16}}{\underbrace{m_O}}\Rightarrow m_X=\mathrm{8,56}$