AP Chemistry 1.4 Forming and Breaking Bonds. What is the correct expression for the equilibrium constant, Keq?
|AP Chemistry||Breaking Bonds|
Forming and Breaking Bonds
|Test Prep||AP Chemistry|
And here are the potential answers:
Okay, okay, maybe we were a little hard on those Jacksons. This one really is as easy
as ABC… D. Can’t forget D. [Jackson 5 in chemistry class and teacher shows A, B, C, D on board]
Anyway, let’s get to our question. The equilibrium constant for any chemical
reaction will always be the concentrations of the products divided by the concentrations
of the reactants, with each species raised to the power of its stoichiometric
coefficient. Yeah, where's your ABC, 123 now, Jackson Five? [Person taking photo's of Jackson 5]
So for this reaction, the equilibrium constant is C times D squared divided by A squared
times B cubed. But wait, there’s more! Call now, and you’ll [Man selling frying pans]
get a second full set of banana-shaped frying pans for free, just pay $89.95 processing
and handling! …Whoops. Sorry for the confusion, that’s
our other job… tough economic times, right?
But there actually is more… There’s an important trick to this question:
we also need to consider the phase of each reactant and product.
Remember that we only include the reactants and products that are in the gaseous state [Reactants and product put inside a box]
in the equilibrium constant. We exclude species that are liquids or solids.
That means we can’t include species C in the equilibrium constant expression.
So, if we revisit our previous expression for Keq but remove species C, which is a liquid, [Species C removed from formula]
we’re left with D squared divided by A squared times B cubed. And that’s choice B, the
correct answer. Now, who wants some banana-shaped blueberry
pancakes? If we’ve learned one thing today, it’s that this is a deal too good to pass [Man selling banana-shaped blueberry pancakes]
up – don’t wait, call now! …Sorry. We have to meet a quota.