If I were to add an oxidizing agent like dilute Potassium permanganate (aq) to a potential fuel such as plastics (polystyrene etc), would the combustion of this fuel be more complete ie: less sooty flame, brighter/hotter flame etc?

  • $\begingroup$ In general, yes (remember self-ignition experiment when a cotton wool soaked in glycerin ignites after a while when sprinkled with solid potassium permanganate). However, you should account for leftovers ($\ce{K2CO3}$, $\ce{MnO2}$) which would add to soot, and if you want to go for a hotter flame, you probably want to look at stronger oxidants. $\endgroup$ – andselisk Aug 29 '19 at 13:53

There is no "if". Unless you add an oxidizing agent, there will never be a flame in the first place. So everybody who starts a flame, without much trouble and possibly without giving it much thought, is already adding an oxidizing agent, and a pretty powerful one: $\ce{O2}$.

With good chances, whatever else oxidant you wanted to add will be worse than oxygen in one or more regards. It will probably be weaker. It will probably carry many times more weight per electron transferred (surely the case with $\ce{KMnO4}$ even you use it solid, and twenty times more so if you dilute it with water; if you thought of diluting it with gasoline, then it just won't dissolve at all). It will produce much more byproducts, maybe including solid ones (again, surely the case with $\ce{KMnO4}$). In short, there are good chances that it will make the flame more sooty and less bright (if maybe more colorful), and the combustion less complete.

Short of these issues, the idea is fine. If you blow fluorine into your flame, I bet it will burn a good deal brighter. The possibility of your survival through this, however, is another story.

The answer would be incomplete without mentioning the two cases when other oxidants, despite not being fluorine, might have an edge over oxygen:

  1. Lower temperature (colder than flame, that is), when kinetics matters a great deal. This covers the case mentioned by andselisk, and also all other cases when you can run a controlled redox reaction in a beaker without much interference from $\ce{O2}$. These, however, are beyond the scope of your question if you want a flame.

  2. Tight packing. Solid oxidants generally beat gaseous oxygen in that you can fit much more of them in a small volume. So if you mix the said permanganate with I'd rather not tell you what, you'll get yourself a decent bomb. The reaction will certainly get more noisy, if not less sooty.

So it goes.

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