00:11
So we have 0 .089 molar sodium hypochlorite.
00:22
And sodium is a spectator in acid -based reactions.
00:26
It's not acid -based active.
00:28
But the hypochlorite ion is the conjugate base of the weak acid, hypocloric acid.
00:38
And so it will react as a base.
00:41
And so i've written the kb reaction, the reaction of hypochloride ion with water.
00:48
The hypochloridion will gain h plus.
00:51
The water will lose it and make oh minus.
00:53
And from the reaction, then, the kb expression.
00:58
Now, you go to the table and you find a ka for hypochlorous acid, but you don't find a kb.
01:09
What you have to do is calculate the kb from the kw.
01:15
And that is based on the relationship that for any weak acid and its conjugate base or a weak base in its conjugate acid, the product of the two equilibrium constants will be kw, only for a pair of conjugates.
01:32
And so the value from the table is 2 .9 times 10 to the minus 8 for hypochloric acid.
01:46
And so now this is like any other problem.
01:50
Once we recognize those things, that sodium is a spectator, so leave it out...