FOOF is a chemical compound that is extremely combustible and dangerous. In researching it, I came across a very difficult to believe factoid:
“Hydrogen sulfide, for example, reacts with four molecules of FOOF to give sulfur hexafluoride, 2 molecules of HF and four oxygens. . .and 433 kcal, which is the kind of every-man-for-himself exotherm that you want to avoid at all cost.”
Is this correct or is it a typo? I have a really hard time believing that just a few molecules reacting could possibly release so much energy. That would mean that a mole of these compounds reacting with eachother would be billions or quadrillions of megatons or some unfathomable number.
Is this really correct? 433 kcal from that reaction?
And a lovely quote from there: “As Lowe points out, the chemistry of this kind of reaction (O[sub]2[/sub]F[sub]2[/sub] and sulfides) is largely unexplored.”
Is it even physically possible to have a reaction between just a few number of molecules result in 433 kcal of energy? Is that more energy than the actual rest mass of the atoms themselves?
I think you (and perhaps the text you quote in your OP) are confusing molecules with moles. As Senegoid’s quote says, it is four four moles of FOOF reacting with one mole of hydrogen sulfide that produces 433 kilocalories. Every mole of a substance contains 6.02214129(27)×10^23 (i.e., Avogadro’s number) molecules of that substance. That is a lot of molecules, a fuckton of molecules, not just a few.
Checking your source, yes the guy you got this from gets it wrong, but he probably assumes that he is talking to other chemists, more or less, who will know that he really means moles.
In fact it is. The mass of the reactants in one molecule of HS and four molecules of F[sub]2[/sub]O[sub]2[/sub] is about 313 amu, which corresponds (via E = mc[sup]2[/sup]) to an energy of 4.67 x 10[sup]-8[/sup] joules, or about 10[sup]-11[/sup] kcal.
Moral of the story: molecules are really small, but Avogadro’s number is really big.
Ok phew! Glad I didn’t just go around believing the… confusing wording of that quote. And glad to see wikipedia got it “right” even though the quote is more confusing itself.
433 kilocalories doesn’t seem like much; a mole of glucose produces 686 kcal per mole when burned with 6 moles of oxygen (58% more); the total weight is about 372, so only a bit higher than the 313 for HS and FOOF; per weight, glucose+oxygen produces 33% more energy (perhaps it is the violence of the reaction that prompts that statement, glucose won’t explode if ignited, not sure about if it was in pure oxygen though, which tends to make many things go boom, if still in need of an ignition source).