GOB Chemistry

Learn the toughest concepts covered in your GOB - General, Organic, and Biological Chemistry class with step-by-step video tutorials and practice problems.

BONUS: Lab Techniques and Procedures

Distillation & Floatation

Distillation and Floatation represent procedures that can be used to separate components of a mixture. 

Mixture Separation

Distillation can be used to separate liquids or gases based on their different boiling points, while floatation can be used to separate solids based on their different densities. 



Distillation and Floatation

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in this video, we're gonna take a look at how do we separate the components of a mixture through to process is known as distillation and flotation. So we're gonna say in order to separate the different components of a mixture, it must be hetero genius. Remember, in a heterogeneous mixture, your salty particles do not dissolve within your solvent. In that way, they do not chemically bond with one another. In this form, each component maintains its individual physical properties. We're going to stay here. Chemical reactions rarely produce a single pure product. So these types of mixtures are very common. Now. One way of separating these components is through distillation. Now, this technique involves the separation of liquids and or gasses based on a difference in their boiling points. Now we're going to say there are many types of distillation methods, but the most common forms are simple and fractional distillation. So here we have two apparatuses set up with one of the left represents a simple distillation process, whereas the one on the right represents a fractional distillation process. So we're gonna take a look at their similarities and also discussed the differences found in both types of apparatuses, and then we'll talk about how What does this help us do now? We're gonna need room guys, let me take myself out of image. So what they both have in common is that they both possess a thermometer. Now, this thermometer is just to record the temperature needed to vaporize one of the components within the mixture. Now, here we have. Our mixture will say that this is a mixture of a plus B, and this is a mixture of a plus B. Okay, we're gonna say here that so both of them have a heating source. So this is a hot plate, and then here we could use a flame. Or we could use a flame from a Bunsen burner. Or we could also use a sand bath. So flame from Bunsen burner, hot plate or heat from is sand about. They both contained flats which have dissolved within them. Two types of liquids. Now, the difference so far between the two is that this one here has this component which isn't discussed in the simple distillation process. We're going to say here that those represent the fractional um, basically our fractional column. Okay, Now, inside this fractional column. We have beats. So these beads helped to increase our surface area and we'll talk about the process and why this is important. So basically what happens here? So you have two different types of liquids dissolved in here. Liquid and liquid Be. Now let's say that liquid a represents methanol, which is C H 30 h. It has a boiling point of about 67 degrees Celsius and liquid be will say his water when the waters H 20 it has a boiling point of 100 degrees Celsius, so water has a higher boiling point. So it Zhar dir to make it vaporizes harder to change it into a gas. So we're gonna do here is we're gonna crank up the temperature. You're gonna crank it up high enough to vaporize the methanol, but low enough so that the water is not getting a prized. So put it around 80 degrees Celsius. Doing that will cause my methanol to get vaporized. And when you're methanol, which is gas is vaporizes gonna move up here just like it moves up here. It's then gonna proceed to go through here. This apparatus is called your leibig condenser. What it does is it exposes the gas that's traveling through this tube to cold water. That cold water causes the gas to condense back into a liquid. So the passing through this condenser, it becomes liquid again, and it's slowly drips down into this collector right here. So when this collector will have just are liquid air methanol, our liquid be, which is our water hopefully gets left behind. Now we're gonna say here that in terms of these tubes were gonna say, Here we have this tube, which is water that's being driven out. So there's a host here, and that hose will connect, maybe toe a sink within your lab. Same thing here. And then there's, ah, host here, which is connected to a faucet within your lab. And that's where the water comes in. Okay, So basically, water is filling here and water is filling here, and the hot gas that's passing through is exposed to this cold water and it condenses down same thing here. The water's cold water will be here. The cold water will be here Now, here in this fractional distillation, the gas has a longer way to travel. It has to pass through all these beats here, giving him or time to get vaporize did. But passing through these beads does two things. It allows it to get vaporized over a longer period and also allows some of that gas to get re condense back down into a liquid. Now, what's happening here is in this process. A and B are both being vaporize Did. But more of a is being vaporized because it has a lower boiling point. And as both are moving up, a gas is they're both getting vaporized. But the temperature isn't great enough to keep water in its gas face of condenses back down into a liquid. So that means that the percentage of this gas that's just gas a is a lot higher than it is for the simple distillation Here in this gas particles that are passing through Ah, small percentage of it is still water. So here we're not only gonna have just we're gonna have a little bit of B is well, but over here because we're doing fractional distillation, which takes longer and is more accurate, we're gonna have a greater percentage of a being isolated at the end so again there dripping down here. Okay, so we're gonna say that in simple distillation. We use this method when both liquids have a boiling point different by more than 25 degrees Celsius. Okay, so this would be a good method for the methanol and water because the differences in their temperature is 33 degrees Celsius now here for fractional. You use that when it's less than 25 degrees Celsius. So let's say if we had ethanol instead of methanol, ethanol and water would be a good combo, because here ethanol has a boiling point of 97 degrees Celsius and water has a boiling point of 100 degrees Celsius. Their numbers air so close that they both get vaporized together. So you would need those beans there to provide more surface area to give ethanol more time to separate itself from the water. Now we're gonna say here that the simple distillation is faster and produces a higher yield. So you get more of this at the end. But here's the thing. Fractional distillation is actually better, because here, by adding beads, you increase the surface area for the gas is to pass through and What you're gonna do here is you're giving it more time to cycle through evaporation and condensation cycles. So you increase evaporation and compensation cycles, which leads to a increase in purity off your product. So you may not make much product, but your product will be a lot more pure. It will be more one component than another. Okay, so you get a higher purity with fractional distillation, not understand this visually, what's going on is remember, we're vaporizing liquids, so we're going from the liquid phase to the vaporization to the vapor phase. So becoming gas and what we have down here is we have our temperature is increasing over time here on the Y axis and here X here means mole fraction. So just think of mole fraction. Think of it as the basically the mass component off your compound within the solution. So what? This graph you're saying? It's saying that initially at a lower temperature at a lower temperature, we're gonna have mawr of my water present than we do our methanol. But as my temperature starts to increase, as we get higher and higher, we're gonna have mawr, the methanol becoming vaporize because again its boiling point is lower, and what's happening here is we're going from the liquid phase up to the vapor phase, so we're vaporizing. And then here. This is also this represents vaporization as we're vaporizing. Look at the totals. It was almost completely water initially, but then slowly but surely look at what's happening. The amount of methanol in the vapor phase is increasing higher and higher over time to eventually where you have solely the methanol at the end. That's a vapor, which will be condensed later on toe. Isolate that liquid. This is an example of fractional distillation how it works. So each one of these here represents a vaporization point, and that's what's causing the amount of methanol to increase in terms of its mole fraction. So just realize that when we're dealing with distillation, we're trying to separate liquids from one another. So we use the fact that they have different boiling points to help us isolate one liquid from another vaporize one, and then later condense it back into its liquid forms so that you have to separate jars or two separate flats with liquids in each. Now, when it comes to flotation, flotation is pretty simple. You have to solids of different densities. So what do you do? You take solid and throw it into a solvent. If it's really dense, it'll fall and sink into the solvent and then solid B, maybe less dense. Soy won't sink. It'll float. So when it comes to flotation, it's a way of separating solids from one another. Based on their differences in density, one will sink. One will float as you guys cover distillation later on. In labs, you'll take a mawr in depth look at the components involved within a simple distillation versus fractional distillation apparatus. Here we're just covering the very basics in terms of it, so you kind of understand what's going on. Later on, when you guys talk about concepts such as collective properties and vapor pressure, you may hear Maura about distillation processes