Is a 80% acethylene 20% oxygene ratio the most explosive?

Question

Hello. I had a discussion with a friend of mine and he says that an 80% oxygen and 20% acethylene ratio is the most ecplosive. Is that right?

Answer 1

Hello Peter D.,

Since there are no materials named acethylene and oxygene, it's difficult to tell. Did you perhaps mean acetylene and oxygen?

In general, for combusting gas mixtures, the stoichiometric mixture for complete combustion is only one proportion which will burn nicely. If oxygen is limited, combustion is likely to be sooty (depending on the particular gases) and slower since some unburned material will be emerging from the bulk to burn whilst mixing with air on the sides. But excess oxygen may also hinder the speed of propagation of the flame front. "Explosive" is an inexact term, so you would have to specify, whether 1) maximal energy release from a given volume at room pressure, or 2) maximal propagation speed of the flame front through the mix, or 3) maximal pressure generated by evolution of exhaust gases, under specified conditions.

That being said -- I do recall a muffler shop in St. Louis that leaked acetylene into the building, and blew up in the early morning. It sounded like a sonic boom, 5 miles away. Not much left of anything there.

This situation is in contradistinction to the situation of burning a solid in pure oxygen -- which burn more ferociously up to about 10 atm of pure O2. Even you, if you were placed in a pressure chamber, and rapidly pumped to 10 atm with pure O2, could burn if ignited -- your living flesh, directly! Most people would find this distressing, but the true scientist would be gratified to confirm the calculation that the energy release by combustion would be much more than sufficient to vaporize tissue water. (combustion 1g dry protein ~ 5.6 kcal, muscle~25% dry mass, heat of boiling off water from body temperature ~ 620 cal/g -- you do the math)

-- Cheers, -- Mr. d.