Question

What volume of oxygen will be required at STP to burn (complete combustion) 250.0 grams of octane (C8H18) in your car’s engine?

Answer 1

Chemical Reaction:

2C₈H₁₈ (g) + 25O₂ (g) ------> 16CO₂ (g) + 18H₂O (l)

By Gay-Lussac's law,

2 volumes of Octane will burn in 25 volumes of Oxygen to produce 16 volumes of Carbon Dioxide and 18 volumes of Water. However, volume of water will be considered 0 because it's in liquid state.

Given Mass of Octane burnt = 250 g

Mass of Oxygen required = (25/2) * 250

= 12.5*250

= 3125 g or, 3.125 kg

I hope this helps.