00:01
Alright, you're calculating the ph of a weak acid solution, a potassium...
00:06
I'm sorry, this is a weak base solution.
00:09
It's potassium nitrate.
00:11
Now, hopefully you know that potassium ions are always soluble, so you really have a nitrite ion floating around that actually can act as a base.
00:20
The potassium ion can't do anything because it's the conjugate of a strong base.
00:25
So what you need to do is take this nitrite ion and make it react with water, which is going to form nitrous acid plus hydroxide ion.
00:35
And that'll be our ice table that we're going to use.
00:37
This is an equilibrium scenario because this is a weak base rather than a strong base.
00:43
Now your problem states that your ka value for the acid is 4 .5 times 10 to the negative fourth.
00:55
Now let's go ahead and turn that into a kb by taking the kw and dividing it by the ka.
01:01
Ka, and remember the kw is 1 times 10 to the negative 14th, and we'll divide that by the 4 .5 times 10 to the negative 4th.
01:11
Let's see what that gives us when we do that.
01:19
All right, i got 2 .2 times 10 to the negative 11th, and that's your kb value.
01:26
Now that's the value that applies to this ice table that we drew here.
01:30
Let's go ahead and put in our initial concentration.
01:32
It's 0 .191 for for the nitrate.
01:35
We'll ignore the water.
01:36
We'll add zero of these initially...