00:01
Okay, so we have 0 .136 molar kno2, and the k of hno2 is 5 .6 times 7 .94.
00:08
So we have a weak base, and we're given the k of a weak acid.
00:17
It's its conjugate acid, so it relates, but again, it's not the same measure.
00:22
So what the k measures is hno's 2 ability to react its water.
00:29
Nuclear reaction to h .o3 plus, plus, n .o2 minus.
00:33
That's not the reaction that's abnormal that's right we don't have hno2 what we have okay is the extent that happens what we have is an o2 minus plus h2o to make oh oh minus plus h and o2 so this reaction of no2's ability to react with water is measured by kb and so the kb is what we want to find is this is the reaction that's happening here and how we really the two is this two different ways the most direct way is k w equals k a times kb and kw is equal to 1 times 10 to n814 that's just a constant it's always going to be true at least within a given temperature range um and so we know what the k a is we know what the kw is we can find the kb through this equation here so let's go ahead do that so take 1 times 10 to the negative 14 divided by our k a which is 5 .6 times 10 to negative 4 and that is equal to 1 .79 times 10 to the negative 11.
01:58
So this is our kb.
01:59
This is the thing that's measuring the reaction care about.
02:03
We don't care about this reaction.
02:04
We want this reaction here.
02:08
So how does kb actually measure this? so kb is just an equilibrium constant and an equilibrium constant is just the product's concentrations.
02:18
And divide by the reacting concentrations.
02:26
You can see i ignore it h2o here because it's a pure liquid.
02:29
They don't take effect in an equilibrium constant.
02:34
Pure liquids don't.
02:35
So why don't we care about the no2 concentration? if we're looking at this and we're trying to find the oh, because from oh, we can go to poh to ph.
02:48
We're trying to find the oh concentration.
02:50
We have two unknowns and two unknowns.
02:52
How do we simplify this? well, if we're looking at this equation, every oh you make will make one h and o2, so one to one...