Slow and Steady?

بسم الله الرحمن الرحيم

Assalamu Alaikum,

I was looking at some kinetic and equilibrium related notes from last semester and I had a reaction written down:

2C6H14 + 19O2 <–> 12CO2 + 14H2O

(in language for Spiderman or non science people)

simple gasoline + air <–> CO2 + water

At room temperature, (and exposed to air=O2) what happens to an open barrel of gasoline?

It just sits there. You don’t see water flying everywhere and CO2 fuming.

But according to my notebook calculations, that reaction is product favored at room temperature. Product favored means that at equilibrium, there is more CO2 and H2O than gasoline. Equilibrium means when the concentrations of both sides of the reaction are not changing anymore. So why isn’t there water flying everywhere when you open the nozzle to fill your car up with gasoline?

And then I remembered I asked something like that in class and my professor looked at me with a half-comical facial expression–(half quoted)

—

Professor: “What did we just learn from last chapter?”

Faith786: “kinetics…?”

Professor: “So the reaction is product favored. What does kinetics tells you about the reaction?”

Faith786: “…”

Professor: “Speed. It is a product favored reaction and will have more products at equilibrium, but it is *slow* to get there.”

—

Having that really weird flashback, I had another appreciation for chemistry gifts moment: What would happen if product favored reactions that ran slow* could go fast or fast reactions could slow down?

(*ran slow/fast: meaning that it gets to equilibrium–be it reactant/product favored–slowly or fast)

Well, you couldn’t drive a car, that is for sure. You would pump out water and stuff you exhale.

But think about this a little more–how would you eat? How long would it take you to digest food if your body didn’t have a relatively quick metabolism? Or if it was too fast, how much food would you have to eat to keep sugar in your body at a stable level?

Would the earth erode faster (if things sped up) or would life fall apart (if things slowed or sped up too much)? Would survival of the fittest work here? Because it would be chemical composition of animal’s bodies, not living habits that would decide if they can exist.

Would we even have food? If reactions ran too slow, maybe nothing would bear fruit or  if it was too fast, the plant cycle would be too fast that we couldn’t pick the fruit/vegetable out to eat, let alone if it would decay before we can digest it with our super slow bodies.

It amazes me how certain reactions run slow and certain reactions get to equilibrium faster. And the world works. If a couple reactions ran too slow or too fast, the earth would evolve in a really REALLY weird way.

Another thing to consider is that what affects reaction rate is temperature. So natural chemical reactions that happen on earth are fast or slow *at the temperature the earth is at*. If the earth was too hot or too cold, that would change reaction speed dramatically. And the earth has a wide range of temperatures but it still works–we still have life, we still have the means to sustain life and it has for many years.

So today’s two-part chemistry gift:

Be grateful that certain chemical reactions run fast or slow and that the earth maintains a temperature range for those reactions to occur at those speeds.

Maybe some of this mad kinetics math is driving me nuts, but I am happy gasoline doesn’t evaporate to CO2 and water droplets at room temperature immediately. And that my body can digest food at a rate that keeps energy in my body but not too slow that I become sluggish or too fast that I have to keep eating all the time.

Well, I should stop eating so much, but that isn’t a kinetics issue– =)

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