The ratio of the mass percentages of ' C & H ' and ' C & O ' of a...

Mass ratio of $C: His4: 1 ⇒ 12: 3$

& $C: Ois3: 4 ⇒ 12: 16$

so $massmolemoleratioC1211H333O1611$

Empirical formula $⇒$${CH}_{3}O$

as compound is saturated acyclic so molecular formula is ${C}_{2}{H}_{6}{O}_{2}$.

${C}_{2}{H}_{6}{O}_{2} + \dfrac{5}{2}{O}_{2} ( g ) ⟶ 2{CO}_{2} ( g ) + 3{H}_{2}O ( g )$
$2$mole $5$mole

so required moles of ${O}_{2}$is $⇒ 5$