Phản ứng cháy: $C_xH_yO_2+\left ( x+\frac{y}{4}-1\right )O_2\overset{t^o}{\rightarrow}xCO_2+\frac{y}{2}H_2O(1)$
Theo (1), ta có : $x+\frac{y}{4}-1=3,5\Leftrightarrow x+\frac{y}{4}=4,5\Rightarrow \left\{\begin{matrix} x=3\\ y=6 \end{matrix}\right.\Rightarrow X:C_2H_5COOH$
Ancol no Y : CnH2n+2-m (OH)m (1 $\leqslant$ m $\leqslant$ n) $\Rightarrow$ este Z : (C2H5COO)mCnH2n+2-m
$\Rightarrow M_{este}=73m+14n+2-m=\frac{8,7}{0,1}m$ hay 14n+2=15m (2)
Mặt khác $d_{Y/O_2}$< 2 hay 14n + 2 + 16m < 64 $\Rightarrow$ 30m + 2 < 64 (vì m $\leqslant$ n) $\Rightarrow$ m < 2,1
Từ (2) $\Rightarrow \left\{\begin{matrix} n=2\\ m=2 \end{matrix}\right.\Rightarrow$ ancol Y : C2H4(OH)2
$\Rightarrow$ Z : C2H5COOCH2CH2OCOC2H5