The complete balanced equation for the below reaction is
C5H9O + O2 yields CO2 +H2O
balanced equation
4 C5H9O + 27 O2 →20 CO2 +18 H2O
that is 4 moles of C5H9O reacted with 27 moles of O2 to yield 20 moles of CO2 and 18 moles of H2O. This reaction when balanced obey the law of mass conversion since the mass of the product is the same to the mass of the reactant.