Solubility and Intermolecular Forces

Why was it so important that we identify a compound is polar or non polar? Well, because we're going to say that compounds with the same inter molecular force or polarity will dissolve into each other toe form a solution. Now we're gonna say that if you have a polar and a polar, they're going to mix together. Well, if you have a non polar in a polar there polarities air different so they won't be able to dissolve into each other to form a solution. Now we're gonna say, according to the theory of likes, dissolve likes. Basically, the two compounds have to have the same inter molecular force. If they have the same inter molecular force, they have the same polarity. But they could also have different inter molecular forces. So let's say one compound had hydrogen bonding and the other one had dipole dipole. That's okay because hydrogen bonding and dipole dipole are both polar forces. So because they're both still polar, they'll be able to dissolve with you one another. But let's say one had dipole dipole and the other one had London dispersion. Dipole dipole is polar. London dispersion is non polar because of their differences in polarity, they will not mix. Also, we're going to say that there is a difference between a mixture and a solution. We're gonna say mixtures. We've talked about this so many weeks ago. Mixtures come in two types we have homogeneous or homogenous or hetero genius. We're gonna say homogeneous mixtures mixed together. They dissolve into each other and we're gonna say that heterogeneous mixtures do not mix oil and water is a good example that we've talked about. They won't mix because why oils are non polar solvents. Their non polar water, on the other hand, is polar. As a result, polar and non polar do not mix. That's why oil and water don't mix together at all. So mixtures come in these two types Ah, solution. All solutions are just homogeneous mixtures. So remember the difference. Mixtures come in two types that can either be hetero genius. What were they mixed together or homogeneous, where they mix together or heterogeneous where they don't all solutions are just homogeneous mixtures. In a solution, we can dissolve both things into each other, so they do mix

For this example, we have to identify the inter molecular forces present in both the soggy in a solvent. Here, it's safe to assume either one is a solid or the solvent and predict whether a solution will form between the two. So again, remember fundamentally, for solution to form, both should be polar or both should be non polar. If they're both the same and polarity, they will mix together to form a solution. If we take a look at the first one, we have CCL four and P four. Well, p four is the easy one. We say that any time we have non metals connected to themselves or by themselves, their non polar by default, if you're non polar, your inter molecular forces London dispersion, that's not as important. Fundamentally, we need to just know if it's polar or non polar here. CCL four. We've drawn this already. Remember Siegel's in the center. It has four valence electrons. We have four chlorine. Each one has seven valence electrons. Central element has no lone pairs, so we use rule one. A central element must be connected to the same elements it is, and central element must be less electro negative than the surrounding elements. So it follows Rule One A and one B. So it's definitely non polar. Yeah, Now, because both are non polar, they will form a solution. We could also say that they both since they're both non polar, they're both London dispersion. So if you have to identify the Inter molecular Force would say both are London dispersion.

for be and B. We have h directly connected to oxygen. So if h is connected to fund, that's h bonding. And remember, h bonding is a polar force. Mhm. Now we have see 686 We've said this also. If your compound has Onley carbon and hydrogen, it's going to be non polar automatically and its force will be London dispersion. But fundamentally, one is polar. One is non polar. They have differences in polarity. Therefore a solution does not form.

for C. We have a lot of carbon and hydrogen is here. We can ignore those parts because here's the major force H is connected to end. Hydrogen bonding is a stronger force than London dispersion because it has aged connected to end here, we're going to say that this is hpe bonding. H bonding is a polar force. Okay. And in this example, we have h connected to F. This is also HB bonding and it's also a polar force. Both are pollers who will definitely make a solution. Now, one thing we need to talk about here is this compound and see has a lot of carbons with it. Let's say we're trying to dissolve Ah, compound that had a lot of carbons in water. What we need to realize here is that the Mork carbons your compound has, the more non polar it becomes. This is an important concept for Kem one. And also for those of you who are gonna take organic one on organic too. We're going to say the mawr carbons associated with the compound the more non polar it becomes and the less soluble it becomes in water, the less of it will dissolve to form a solution. We're gonna say the cut off is once you get upto five carbons or higher, that compound becomes very non polar and it becomes incredibly difficult to dissolve it in water. So if we're looking at two compounds ch three c h two ch two ch 20 h and Ohh ch two ch two c h two c h 20 H. And your professor wanted you to determine which one is more soluble in water. We're gonna say both have the same number of carbons. Both have four carbons. So there's somewhat dissolvable in water because water, it's inter molecular forces h bonding. And here we have hte connected toe O h connected to O H connected toe. So part of this compound does have h bonding. That's what makes it soluble somewhat in water. Now we're gonna say that the second structure is more soluble because the second structure has Maura wages. So the mawr O H is you have the more NHS you have, the more HFS you have, the more H bonding you'll possess And the more H bonding you possess, the more you'll be able to dissolve in water So if we're comparing these two weeks, say the second one is more dissolvable in water. Now let's say we had C H 30 h or CH three ch two h Okay, Both have a weight, so both have H bonding. But the second structure has mawr carbons, so it's less soluble in water. The top one has H bonding because of the O. H. And it only has one carbon, so it would be more soluble. So just make a little note on this. The more carbons we have, the more non polar the mawr, o h n h and H F, the more H bonding you'll possess and the more soluble you'll be in water.

Now let's look at this Final One D. So we're gonna say, Let's look at the easier one. We have h connected to end here. So it's going to be HBO bonding for its inter molecular force, which is a polar force. But now we have to figure out what the heck is the force and I f four minus here. It's not easy to see, so we have to draw it out and we have to draw because we know it's not Ionic. We know it doesn't have a bonding, so it's not one of those two. This compound is gonna either be dipole dipole if it's polar or London dispersion. If it's non polar now, the only way we can tell that is if we draw it out. So I will go in the center because I is less electoral negative. I is in group 78 so it has seven Valence electrons. Then we have four Florence, Florence and groups seven A. So it has seven valence electrons, flooring. Onley makes one bond. So they go the bonds now also remember that minus one means what minus one means we gain another electron. So we're gonna add one more electron to the mix. Okay, So 123 There was one here also. Okay, so we're gonna say, How many electrons do we have left? We have on unpaid electron here, here, and these two are paired up. So you see those two electrons that are separated Bring them close together. We should pair up our lone pairs. So there they go. So we have to lone pairs. Now we go over the rules. It has lone pairs around the central element. So we're gonna use the rules for rule to. So first, the central element must be connected to the same elements. Aydin is only connected to florins to the central element. Must be less electoral negative. The central element is less electoral negative. So it follows to be to see we use dipole arrows to point to the more electro negative element. So this type of arrow points to flooring. It gets canceled out by this dipole era which has in the opposite direction. This type of arrow points to flooring and it gets canceled out by this type of arrow that points to the other flooring. So all our element dipole arrows cancel out then we have a lone pair, diaper arrow that points this way and one that points the opposite way, so they also cancel each other out. So based on all the rules for rule to this compound is non polar. And because this element is non polar, its forces London dispersion. But here's the most important thing. One is non Poland. One is polar because their differences in polarity no solution is formed. So that's what we'd say for a part deep now. Hopefully, guys are working towards being able to draw these compounds faster and being able to identify the inter molecular force. When it comes to solutions for the solution of form, both compounds need to be polar or both need to be non polar likes, dissolve likes. Now that we've seen this, I want you guys to attempt to do this practice question on your own. So in this one, we have to figure out which of the following statements is our true meaning. That one could be the correct answer, or more than one answer could be the correct answers. So go over what we know about inter molecular forces about polar and non polar and I'll give you guys a huge hint if it ends with a nine methane plantain. All that means is that compound is what we call an al cane. Al canes are compounds with Onley, carbon and hydrogen, and that should be a huge hints. Keep your compound has only carbon and hydrogen. What can you say about its polarity? Is a polar or non polar?

Which of the following statements is/are true?

a) Methane will dissolve completely in acetone, CH₃COCH_3.

b) Hydrofluoric acid (HF) will form a heterogeneous mixture with tetrachloride, CCl₄.

c) Pentane will form a homogeneous mixture with CBr₄.

d) Methanethiol (CH₃SH) is miscible in fluoromethane (CH₃F).

• A. A
• B. B & C
• C. C & D
• D. B,C, & D