Answer
225.5 mol O₂
Procedure
Assuming the complete combustion of heptane, we will consider the following reaction for our calculations.
C₇H₁₆ + 11 O₂ → 7 CO₂ + 8 H₂O
The moles of oxygen can be determined by stoichiometry
[tex]20.50\text{ mol C}_7\text{H}_{16}\frac{11\text{ mol O}_2}{1\text{ mol C}_7\text{ H}_{16}}=225.5\text{ mol O}_2[/tex]