00:01
Okay, so we want the molarity and the molality of a solution.
00:06
Okay, so let's first start by computing the molarity.
00:12
So molarity will be number of moles divided by the volume of the solution in liters.
00:20
So the first thing we need is the number of moles, right? the number of moles of ammonia.
00:29
Okay, so we have 30 grams of ammonia.
00:35
Okay, and to compute number of moles, basically you need to use the molar mass.
00:41
If you look that up, one mole of ammonia will have 17 grams.
00:52
Okay, if you compute that, cancel the grams, final units will be mole, which is what we want.
00:59
You will have something like 1 .76 mole.
01:07
Okay, first step done.
01:11
We also need the volume of the solution.
01:15
Okay? and we don't really have that.
01:17
What we have is the density of the solution and the mass of the solvent, which is the water, and the mass of the ammonium.
01:25
So we can compute the mass of the solution.
01:30
And using the density then, we can arrive at the volume of the solution.
01:36
Okay, remember the density connects mass and volume.
01:40
So let's do that.
01:42
So now our destination is the volume of the solution.
01:50
That's what we want.
01:52
So first, we need to compute the mass of the solution.
01:57
So the mass of the solution will include 30 grams of ammonia right here.
02:04
And we have also to include, of course, the 70 grams of water.
02:11
Okay.
02:13
Now, this will give you...