00:01
In this question, you want to determine the molecular mass of the polymer.
00:04
We want to use the van hofz equation where the osmotic pressure equals c, concentration, multiplied by the constant, t, which is the temperature in kelvin, and divided by molar mass.
00:24
This is what we want to find out.
00:26
So if you rearrange it, you can see that osmotic pressure divided by the, concentration equals r t and divide by m so this tells us that um if you plot a osmotic pressure divided by c as y x and then you have x which is c concentration it should give you a straight line and we know that the intercept will be r t divided by m and the slope will be account for the non -ideal, but we assume it's negligible for this problem.
01:18
So this is going to be y equals mx plus b.
01:27
The intercept will be b.
01:29
M is the slope.
01:31
And again, as i just mentioned, this is non -ideality, non -ideality.
01:43
All right, so now let's say we have.
01:46
To calculate x and y.
01:48
For each c, x, you have a y, osmotic pressure divided by c.
01:54
So say the first one is 8 .10, then you have a pi divided by c of 8 .1.
02:08
Let me do the mass for you.
02:12
8 .40 times 10 to negative 4 divided by 8 .10.
02:18
This will give you a 1 .037 times 10 to negative 4.
02:24
The second data point 12 .31, you do the same.
02:30
1 .72 times 10 to negative 4 divided by 12 .31, you end up having 1 .397 times 10 to negative 4...