All right, guys, so let's go ahead and talk about one of the most important topics in
thermodynamics, which is using bond dissociation energies to calculate the enthalpy of a reaction.
Bond dissociation energies are values that are going to describe the strength of chemical
bonds.
Now, in chemistry courses that are way beyond the level of this course, organic chemistry,
we actually can use math to figure out exactly why two atoms have the exact strength of bond
that they do.
But in this course, you're never going to be asked that.
You're never going to be asked to explain why the bond between H and H is 436 kilojoules
per mole.
That's not going to happen.
So these are going to be basically experimental values that you're going to be given that
you're going to use as reference to just figure out one question: is this going to be an exothermic
reaction or is this going to be an endothermic reaction?
Now, keep in mind, just because we know the enthalpy, doesn't mean that we actually know
the spontaneity.
Remember that the enthalpy is just one component of the spontaneity.
We're also going to need to know the temperature and the delta S. But for right now, all we're
worrying about is the delta H.
We're just saying is this exothermic or endothermic?