Hướng dẫn :  \[{{n}_{C{{O}_{2}}}}={{n}_{{{H}_{2}}O}}=0,2\text{ mol; }{{\text{m}}_{{{O}_{2}}\text{ pha }\!\!\hat{\mathrm{u}}\!\!\text{ n  }\!\!\ddot{\mathrm{o}}\!\!\text{  }\!\!\grave{\mathrm{u}}\!\!\text{ ng}}}={{m}_{C{{O}_{2}}}}+{{m}_{{{H}_{2}}O}}-{{m}_{X}}=8\text{ gam }\to {{n}_{{{O}_{2}}\text{ pha }\!\!\hat{\mathrm{u}}\!\!\text{ n  }\!\!\ddot{\mathrm{o}}\!\!\text{  }\!\!\grave{\mathrm{u}}\!\!\text{ ng}}}=0,25\]

${{n}_{O\left( X \right)}}=0,1\text{ mol }\to \text{ }$ Trong X, \[{{n}_{C}}:{{n}_{H}}:{{n}_{O}}=2:4:1\]  hay X là C₄H₈O (metyl propionat)