00:01
In this solution problem, i'm starting with 75 milliliters of a certain solution.
00:06
And it helps to think about what's happening here.
00:10
So i have 75 milliliters.
00:14
Here in blue, there's my 75 millimeters.
00:17
It contains some amount of solutes.
00:21
Let's say that this is my solute, using eight solute particles there.
00:28
And what's going to happen is i'm going to add solvent, personally water, for example.
00:35
And what that will do is it will increase the volume of my solution.
00:40
So we're told that we're increasing from 75 to 400 milliliters.
00:49
So i'm increasing the volume.
00:52
There's a lot more liquid in here now.
00:54
But i should not change the amount of solutes.
00:58
In fact, i'm going to draw the same number of solute particles that are now spread out over a larger volume.
01:08
So our concentration should decrease.
01:15
And it should decrease by a factor that compares the two volumes to each other.
01:23
So if i'm starting with 3 .5 molar, i'm going to decrease by a factor of 75 milliliters to 400 milliliters.
01:38
Notice that this fraction is less than one, so that is going to reduce my concentration to 0 .656...