00:01
Here we're looking at a remote atmosphere.
00:02
We're finding out ammonia is in the atmosphere.
00:06
And i agree with the clear beam, it makes 10 to the negative four molar in h3 in our rainwater.
00:12
What is the ph of this rainwater? and i included the pkb of ammonia.
00:17
Let's write that clear pkb is equal to 4 .75.
00:22
So i look this up, you should have some access to it.
00:25
You could find the p .a and then convert to pkb, but it should be about 4 .75.
00:30
And another thing, when it says 10 to the negative 4, what that means is 1 times 10 to the negative 4.
00:35
The one is sometimes left off for convenience.
00:38
So this is our concentration ammonia, and this is the pkb of ammonium.
00:42
So what chemically is happening in the rainwater? we have our ammonium, and we have our water.
00:49
What's going on? well, ammonia is a weak base, so it takes up one of those protons.
00:55
And so that makes nh4 plus and also makes oh minus.
00:59
So an h4 plus is a weak acid, but which minus is a strong base.
01:03
And so this is what's driving the basic nature of our weak base.
01:06
This is the base within the weak base.
01:10
And what defines that is the kb.
01:12
Kb is a measure to the extent of which just happens.
01:17
So this is essentially an equilibrium, and kb is a measure of the equilibrium.
01:24
And so kb, like any other equilibrium, is a measure of the products.
01:35
Divide by the reactants.
01:39
And we're going to leave h2o off because it's a pure liquid, and we don't incorporate pure substances into our k expression.
01:48
So we have nhkv equals nh4 plus times oh minus over nh3.
01:54
All right, so if we're looking at this, we have an nh3 concentration.
01:58
So we have that...
