AP Chemistry Investigation #5: Chromatography Paper.

Hi in this video I'm going to show you how you can separate the components of a mixture of different compounds, using chromatography paper, let's discuss the theory and the objective of this experiment. And then we will come back, and I will show you the details on the experimental procedure. Okay.

So chromatography is one of the separation techniques that we can use to separate mixtures components from each other. Now we have discussed in the theory. The following example, where we have a mixture of.

Four different components, a B, C and D. And then we will run the chromatography paper on this mixture to see the separation. Now we have discussed two factors. The first one is the affinity to paper.

And the second one is the affinity to the solvent. Now paper is called the stationary phase. And the solvent is called the mobile phase paper is called the stationary phase, because it doesn't move and solvent is the mobile phase because it moves across the paper.

Now in this example, we can see that a has. Moved the slowest on the paper and B has moved the fastest on the paper. In this case, what do what we can say regarding the affinity to paper? We can say that a has the strongest affinity to paper and V has the lowest affinity to paper. Now regarding the affinity to the solvent, we can say that B has moved the fastest with the solvent. And therefore it has the highest affinity to the salt. However, a way moving slowly with the solvent.

And therefore, the affinity to the solvent is very weak. So in today's. Example, we have a mixture of three dice. Now we have the blue dye, which is called the blue one, the red dye, which is called the red forty and the yellow dye, which called the yellow five.

We are going to use five different solvents. And this is the cellulose molecule that represents the paper. Now in order to discuss the affinity to the paper and affinity to the solvent, we will be using the intermolecular forces concept. And therefore now, by looking at the structure of every molecule, we will be able to.

Tell the type of intermolecular interactions that the molecule can carry on with the solvent and with the paper, if the intermolecular interactions are strong with the paper, for example, then the affinity to the paper will be high if the intermolecular interactions are strong with the solvent, the affinity to the solvent will be high now looking at these different molecules, let's start with the blue one. For example. Now, looking at the blue one, the blue one has three sulfonate ions now sulfonate ions. They can interact with the paper, which has hydroxyl s, and which is considered as a polar molecule.

You can have an ion dipole interaction with the paper, which is a strong interaction. Moreover, you can have hydrogen bonding between the nitrogen here in the blue dye. And the hydrogen here on the oxygen. So basically you can have a strong interaction with the paper. Now the interaction will not be as strong as the red example because rat can hydrogen bond where the paper and also can have the ion. Dipole interaction and also the dipole interaction with the paper.

Now for the yellow, it has the ion dipole. It has the hydrogen bonding because of the O agent here and also because of this carboxylate. So it will have a strong interaction with the paper.

Now, which one will have the stoniest interaction with the paper. You will judge it based on the separation. So the one that will move the slowest on the paper. It means it has the highest affinity to the paper now, looking at the different.

Solvents, we have humane ethanol, 2-propanol water and acetone. Now from these five solvents, we can see that ethanol, 2-propanol and water. They can carry hydrogen bonding where the dyes, and therefore they will have strong interaction.

Now humane is a non-polar molecule, and it will only carry on London dispersion force, or when the cross force with the molecules. Now acetone is a polar molecule. It can carry on dipole-dipole interaction. But also the oxygen in the acetone can carry on hydrogen.

Bonding with the hydrogen's of the hydroxides in the yellow dye and the red dye. So basically now after running your experiment and looking at the separation on your paper, you will be able to have a better judgment or justification on the intermolecular and choose between the molecules and the solvents or the molecules and the paper. Now, one more thing that we will need to measure when we finish our experiment is what is called the retention factor.

Now, the retention factor, which we call our app.It's equal to now, if you look at this image in here, you can see it's equal to d1 and divide it by d2. Now, d1 is the distance travelled by the dye from the starting point, which is this one to where it traveled. And this is d1. Now d2 is the distance traveled by the solvent from the starting point until the end point and therefore d1 will always be smaller or equal to d2. And therefore, our F has to be always smaller or equal to one molecule with high affinity to the paper will have a small RF and. Molecules with high affinity to the solvent will have high RF now let's go back to take a look on the experimental procedure for this investigation, great. So now that we know the objective of our experiment, and we have an idea how the separation will work on the chromatography it's time.

Now to run our experiment, we are given a mixture of three dyes. Now, since the three dyes are blue red and yellow, the mixture will look a green. Now, what we have to do, we will put our mixture on the paper, and we will. Run the paper and look at the separation, but before that we will need to prepare our paper for day in the paper it's easy. But it has some specific details that we have to watch for the very first thing that we have to do if you have to make sure that the socking line on the paper, it doesn't touch the solvent inside the beaker and that's, why we will draw our starting line a little high around one centimeter. We will draw a tick in the middle of the line, just to make sure that this is where we. Are going to put our mixture next to make sure that the solvent will run straight up on the paper.

You will be cutting the corners of the paper, small cuts for the corners, just to make sure that the solvent will run up straight. And this is how the paper look up the small corners now that our paper is ready because we have five solvents. We will make sure to write down on the top of the paper, the name of the solvent. In this case, for example, I would say acetone.

So in here I will say acetone now, I. Need to add the mixture to the paper. And in this case, what I can do I can just take one or two drops or one drop of my mixer, I don't need more than this. Then I'll take small is possible, pipette and I won't, just make sure that I have some of this in mind. Some mixture inside the pipe, add this much. Now all I have to do is to make sure to place the mixture on my paper this way.

So as you can see in here, the spot is not very big, and it's, not very small at the same. So now that I have prepared my. Paper all what I can do now is using a graduated cylinder. I will take around 10 millimeters of the solvent say, for example, take 10 milliliters around 10:00. Now, I can either use a beaker or I can use a chromatography paper jar.

Now if I use the beaker I, add the solvent to the beaker and all I have to do I'll place the paper inside the beaker and watch for the migration of the solvent on the paper. Okay. So now that I have waited enough time for the mixture to separate on the chromatography paper as.

You could notice there is only one solvent where the separation works in a perfect way. So now that I have the separation all I have to do I have to make sure to dry my paper. So the solvent doesn't go above the end line. Now, using a heat gun, you can draw your paper and make sure to be careful when using the heat gun. And now that I have dried, my paper I can take the paper. And of course, I know where my end line is I can just measure the distance traveled by the solvent and I can also measure the.

Distance traveled by the by each die and therefore calculate the R app for each die. I. Hope, this video is helpful to you, I'll.

See you next time.

Dated : 22-Mar-2022