${{m}_{O}}=0,7681.35,4=27,191g$

${{m}_{{{O}_{2}}}}=35,4-14,6=20,8g$

$\Rightarrow {{m}_{O(X)}}=6,391g\Rightarrow {{n}_{O}}\approx 0,4mol$

$\left\{ \begin{matrix}C{{O}_{2}}:x\text{ }(mol)  \\{{H}_{2}}O:y\text{ (mol)}\end{matrix} \right.$

$\Rightarrow \left\{ \begin{align}  & 44x+18y=35,4 \\  & 12x+2y=14,6-6,391 \\ \end{align} \right.$

$\Rightarrow \left\{ \begin{matrix}   x=0,6mol  \\   y=0,5mol  \\\end{matrix} \right.$

$\Rightarrow x:2y:z=3:5:2$

$\Rightarrow {{\left( {{C}_{3}}{{H}_{5}}{{O}_{2}} \right)}_{n}}$