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And so therefore, the net dipole of SO2, based on the way it's drawn, the net dipole moment is downward, which points towards the oxygen atoms. So therefore, because SO2 has a net dipole moment, it is a polar molecule. Now, because SO2 is polar, that means that it's going to have dipole-dipole interactions. The sulfur ... | Dipole Dipole Forces of Attraction - Intermolecular Forces.mp3 |
The sulfur atom is partially positive with respect to the electronegative oxygen atoms, which are partially negative. So if we draw a picture, let's say this is the sulfur atom and these two are the oxygen atoms. Let me use a different color to indicate it. So let's use yellow for sulfur and red for oxygen. So the sulf... | Dipole Dipole Forces of Attraction - Intermolecular Forces.mp3 |
So let's use yellow for sulfur and red for oxygen. So the sulfur atom has a partial positive charge and the oxygen atoms contain a partial negative charge. So now this is going to be attracted to another sulfur dioxide molecule. So the sulfur of one molecule is attracted to the oxygen atom of another. And so that inter... | Dipole Dipole Forces of Attraction - Intermolecular Forces.mp3 |
Hi. It's Mr. Andersen and this is chemistry essentials video 60. It's on driving non-spontaneous processes. Again those are processes that don't occur without external energy. We also call them thermodynamically non-favorable. Sometimes we call them endergonic. But if we were to look at a free energy diagram like that ... | Driving Nonspontaneous Processes.mp3 |
Again those are processes that don't occur without external energy. We also call them thermodynamically non-favorable. Sometimes we call them endergonic. But if we were to look at a free energy diagram like that we're essentially looking at an uphill reaction where we have a positive delta G. If we shove on it, it's ju... | Driving Nonspontaneous Processes.mp3 |
But if we were to look at a free energy diagram like that we're essentially looking at an uphill reaction where we have a positive delta G. If we shove on it, it's just going to return to where it was before. And so how do we lift that? In other words how do we lift that when the reactants actually have less free energ... | Driving Nonspontaneous Processes.mp3 |
Well there's two ways that we can do that. First of all we could add energy from the outside. So this is just a model, but if we add energy from the outside then we can lift those reactants and eventually have the energy of the products. Where is that energy coming from? It could externally come from electricity. For e... | Driving Nonspontaneous Processes.mp3 |
Where is that energy coming from? It could externally come from electricity. For example when we're charging a rechargeable battery. Or it might even come from the sun. And so that's how a solar panel works or how a leaf works if we're looking at photosynthesis. Another way we can do it is we can couple it to a spontan... | Driving Nonspontaneous Processes.mp3 |
Or it might even come from the sun. And so that's how a solar panel works or how a leaf works if we're looking at photosynthesis. Another way we can do it is we can couple it to a spontaneous process. And so if we were to look at an exergonic or an energy releasing process like this where a delta G is less than zero, t... | Driving Nonspontaneous Processes.mp3 |
And so if we were to look at an exergonic or an energy releasing process like this where a delta G is less than zero, that's going to be a downhill reaction. So you could imagine if we were to couple those two together, and again this is just a model, then we could take some of that energy released in that spontaneous ... | Driving Nonspontaneous Processes.mp3 |
So our goal is to make it a negative value. In other words make this spontaneous. And we can do that in one of two ways. We can take energy in from the surroundings. So for example if we use electricity, like when we're charging a battery, then we can change that delta G to a negative value. Likewise if we were to take... | Driving Nonspontaneous Processes.mp3 |
We can take energy in from the surroundings. So for example if we use electricity, like when we're charging a battery, then we can change that delta G to a negative value. Likewise if we were to take in light, for example in photosynthesis, we can turn that upside down as well. We can also couple it to another reaction... | Driving Nonspontaneous Processes.mp3 |
We can also couple it to another reaction or to another process. So for example in our body we constantly do this using a molecule called ATP. Every time we convert ATP into ADP we release a little bit of energy. And we use that to do things like think and move and talk. And so let's start with the electricity. So if w... | Driving Nonspontaneous Processes.mp3 |
And we use that to do things like think and move and talk. And so let's start with the electricity. So if we're looking at a battery like this, why does a battery eventually run out? It's because our reactants had more energy than our products do. And so we're losing that energy. Now we're using that to do work. We're ... | Driving Nonspontaneous Processes.mp3 |
It's because our reactants had more energy than our products do. And so we're losing that energy. Now we're using that to do work. We're using it and losing it as thermal energy. But eventually you have a battery that doesn't work. And so how am I going to recharge it? I have to connect it to electricity. | Driving Nonspontaneous Processes.mp3 |
We're using it and losing it as thermal energy. But eventually you have a battery that doesn't work. And so how am I going to recharge it? I have to connect it to electricity. And what that electricity can do is it can actually turn those products into reactants and then add energy to them. And we can recharge that bat... | Driving Nonspontaneous Processes.mp3 |
I have to connect it to electricity. And what that electricity can do is it can actually turn those products into reactants and then add energy to them. And we can recharge that battery. So we can use it over and over again. Likewise if we look at life on our planet, most of us are heterotrophs. What does that mean? We... | Driving Nonspontaneous Processes.mp3 |
So we can use it over and over again. Likewise if we look at life on our planet, most of us are heterotrophs. What does that mean? We take energy in our food. So we take energy in our food, for example like in glucose. We combine it with oxygen. We make carbon dioxide and water. | Driving Nonspontaneous Processes.mp3 |
We take energy in our food. So we take energy in our food, for example like in glucose. We combine it with oxygen. We make carbon dioxide and water. But when we do that the reactants, in other words our food and our oxygen have a higher amount of free energy than the products that we produce. And so we would be stuck i... | Driving Nonspontaneous Processes.mp3 |
We make carbon dioxide and water. But when we do that the reactants, in other words our food and our oxygen have a higher amount of free energy than the products that we produce. And so we would be stuck if it weren't for the autotrophs. If it weren't for plants. What they can do is turn that backwards. In other words ... | Driving Nonspontaneous Processes.mp3 |
If it weren't for plants. What they can do is turn that backwards. In other words they can take that carbon dioxide and water and they can add energy to it. Now where are they getting the energy from? They're getting it from the sun. And so how does photosynthesis work? Well inside a leaf you have chloroplasts. | Driving Nonspontaneous Processes.mp3 |
Now where are they getting the energy from? They're getting it from the sun. And so how does photosynthesis work? Well inside a leaf you have chloroplasts. And inside the chloroplasts you have a membrane like this. And what it's doing is it's taking in energy from the light. What's it doing with that energy? | Driving Nonspontaneous Processes.mp3 |
Well inside a leaf you have chloroplasts. And inside the chloroplasts you have a membrane like this. And what it's doing is it's taking in energy from the light. What's it doing with that energy? It's getting its electrons excited. It's passing those electrons down an electron transport chain. And eventually those high... | Driving Nonspontaneous Processes.mp3 |
What's it doing with that energy? It's getting its electrons excited. It's passing those electrons down an electron transport chain. And eventually those high energy electrons go back into your food. Now who are they making that food for? Themselves. Because they're going to do that same process of respiration. | Driving Nonspontaneous Processes.mp3 |
And eventually those high energy electrons go back into your food. Now who are they making that food for? Themselves. Because they're going to do that same process of respiration. Now where does a lot of that energy go? A lot of that energy goes to this molecule right here, ATP, which is used in energy coupling inside ... | Driving Nonspontaneous Processes.mp3 |
Because they're going to do that same process of respiration. Now where does a lot of that energy go? A lot of that energy goes to this molecule right here, ATP, which is used in energy coupling inside our body. And so again we're using external energy to turn that endergonic reaction upside down. Now that's one of onl... | Driving Nonspontaneous Processes.mp3 |
And so again we're using external energy to turn that endergonic reaction upside down. Now that's one of only two ways that we can do this. We can also energy couple. And so what's going on there? We're taking an endergonic reaction and coupling it to an exergonic reaction. Or pairing a non-spontaneous with a spontaneo... | Driving Nonspontaneous Processes.mp3 |
And so what's going on there? We're taking an endergonic reaction and coupling it to an exergonic reaction. Or pairing a non-spontaneous with a spontaneous reaction. So inside our body the molecule that we use over and over and over again is going to be ATP or adenosine triphosphate. And on the end it has these three p... | Driving Nonspontaneous Processes.mp3 |
So inside our body the molecule that we use over and over and over again is going to be ATP or adenosine triphosphate. And on the end it has these three phosphate molecules. And as this last phosphate pops off it releases energy with it. And so that's going to be a spontaneous reaction. It's releasing energy. But then ... | Driving Nonspontaneous Processes.mp3 |
And so that's going to be a spontaneous reaction. It's releasing energy. But then we can break our food down. And as we do that, that releases energy which we can use non-spontaneously to create more ATP. And it's said that you go through your whole body weight in ATP every day. Now what do we use that ATP to do? We us... | Driving Nonspontaneous Processes.mp3 |
And as we do that, that releases energy which we can use non-spontaneously to create more ATP. And it's said that you go through your whole body weight in ATP every day. Now what do we use that ATP to do? We use it to couple to non-spontaneous reactions inside our body. So for example how do your nerves work? If we loo... | Driving Nonspontaneous Processes.mp3 |
We use it to couple to non-spontaneous reactions inside our body. So for example how do your nerves work? If we look at the lining of a nerve or the membrane of a nerve, we have the spontaneous release of the phosphate as we break down ATP. But we're using that for a non-spontaneous movement of ions inside and outside.... | Driving Nonspontaneous Processes.mp3 |
But we're using that for a non-spontaneous movement of ions inside and outside. If we were to look at a muscle, what we're doing is that spontaneous release of the phosphate is coupled to a non-spontaneous contraction of that muscle fiber. And so again, it's not like we're using electricity. It's not like we're using l... | Driving Nonspontaneous Processes.mp3 |
This person says NH3 is a reactant and therefore should be a factor, but again they're not understanding about the rate determining step. This person says that it should increase because there are more faster stronger collisions. Again all of these are misconceptions. All right the next part, part c, is the student's d... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
All right the next part, part c, is the student's diagram which shows going from reactants to products. Is it consistent with the enthalpy? Now the enthalpy is negative. The enthalpy change is negative so this is an exothermic process. So the answer is no because the overall reaction is exothermic as indicated by the n... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
The enthalpy change is negative so this is an exothermic process. So the answer is no because the overall reaction is exothermic as indicated by the negative delta H. The products should be lower in potential energy than the reactants. As the reactants convert to lower potential energy products, energy is released. So ... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So we have to disagree and say no. No, delta H is negative. The arrow should be going from reactants to products as in going down not up. No because the overall reaction is exothermic and loses energy whereas the diagram implies it's endothermic. Okay these are all good answers. No, based on the negative enthalpy the r... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
No because the overall reaction is exothermic and loses energy whereas the diagram implies it's endothermic. Okay these are all good answers. No, based on the negative enthalpy the reaction is exothermic and that's not reflected in the diagram which shows a higher amount of potential energy for products than reactants.... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
All right here's some misconceptions. This person says yes because all the reactants and products are in the correct place. This person says yes since the reactants of the combined steps are at the bottom and the products are included. So again these are misconceptions. All right next part we're going to talk about the... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So again these are misconceptions. All right next part we're going to talk about the types of intermolecular forces and that includes London dispersion forces. Dipole-dipole forces because these molecules are both polar. They are definitely asymmetrical in which the bond dipoles are not going to cancel out and they hav... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
They are definitely asymmetrical in which the bond dipoles are not going to cancel out and they have hydrogen bonding attractions. They experience hydrogen bonding attractions. Again they experience hydrogen bonding attractions with other molecules because they contain a hydrogen directly bonded to an oxygen. So all th... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So all three of these IMFs would be experienced. LDFs, dispersion forces, dipole-dipole, and hydrogen bonding. Okay so we have a nice list. You can say LDF for short that's fine. LDF, dipole-dipole, hydrogen bonding. You can write them out. You can abbreviate. | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
You can say LDF for short that's fine. LDF, dipole-dipole, hydrogen bonding. You can write them out. You can abbreviate. Looks good. Okay so this is a good example of a type of intermolecular force. Looks good. | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
You can abbreviate. Looks good. Okay so this is a good example of a type of intermolecular force. Looks good. Now if you said London dispersion forces and hydrogen bonding, I would accept that as well. Both have a special form of the dipole-dipole force known as hydrogen bonding. Okay sounds good. | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
Looks good. Now if you said London dispersion forces and hydrogen bonding, I would accept that as well. Both have a special form of the dipole-dipole force known as hydrogen bonding. Okay sounds good. But they never did mention LDFs. So if you're going to mention all of the intermolecular forces you have to be complete... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
Okay sounds good. But they never did mention LDFs. So if you're going to mention all of the intermolecular forces you have to be complete. So just to be on the safe side it'd be good idea in this case to say London dispersion forces, dipole-dipole forces, and hydrogen bonding. Again it'd be a discussion at the reading ... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So just to be on the safe side it'd be good idea in this case to say London dispersion forces, dipole-dipole forces, and hydrogen bonding. Again it'd be a discussion at the reading whether or not dipole-dipole forces be required because again many teachers explain that hydrogen bonding is a special kind of dipole-dipol... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
This person says that CH3OH has dipole-dipole and London forces but they never actually said they left off the part about hydrogen bonding. And then a little more cause for concern down here because they're including things like ionic bonds. Okay so again some misconceptions and incomplete answers on this page. All rig... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
All right when an equimolar mixture of the two compounds is heated to 50 degrees celsius in distillation, the vapor phase contains a higher mole fraction of CH3OH molecules. So that means that it's essentially saying it's easier for CH3OH to go from a liquid to a gas. The fact that there is a higher mole fraction of mo... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
And this molecule has a larger electron cloud because there are two oxygens as opposed to only one oxygen on the right. So larger electron cloud means you could talk about London dispersion forces. Also with two oxygens you have two opportunities to form hydrogen bonding interactions. So you could have talked about tha... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So you could have talked about that there is an extra spot for hydrogen bonding. That would indicate that there are should be stronger intermolecular attractive forces which the HCOOH has a little bit more than the CH3OH. Okay so you could have said CH3OH must have weaker intermolecular forces than HCOOH. HCOOH has gre... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
HCOOH has greater dispersion forces because it has a larger more polarizable electron cloud due to the extra oxygen atom. Or the polarity of the CO bond in the HCOOH molecule provides another region of partial negative charge that can attract the slightly positive H atom in a neighboring molecule. So again extra opport... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
Okay here are some student answers. This person talks about the extra oxygen and the polarizability and the stronger intermolecular forces related to that LDF, London dispersion force. This person says two oxygen atoms so therefore we're looking for an extra amount of spots for hydrogen bonding. So having only one oxyg... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So having only one oxygen reduces the number of hydrogen bonds. All right here's some concerns and misconceptions. There is hydrogen bonding in HCOOH while CH3OH does not have hydrogen bonding. Okay so that's a problem. And then this person says it shows that the IMFs of CH3OH are weaker and easier to break and mention... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
Okay so that's a problem. And then this person says it shows that the IMFs of CH3OH are weaker and easier to break and mentions dipole-dipole forces that are somehow present in one molecule but not in the other. As if somehow only one molecule has dipole-dipole forces. So again some some misconceptions there. All right... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
So again some some misconceptions there. All right now I want to make a very important point about this next part because of something I saw on one of the students responses. Okay we're looking at a titration experiment. In unit four we have things like stoichiometry, reactions, titration, acid-base reactions. All of t... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
In unit four we have things like stoichiometry, reactions, titration, acid-base reactions. All of this is fair game for a question like this. Okay we're given a balanced chemical equation we're talking about a titration experiment. Now there is other stuff about acid-base titration and weak acids and weak bases that is... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
Now there is other stuff about acid-base titration and weak acids and weak bases that is mentioned in unit eight. But you should definitely be able to do the information in unit four and therefore answer a question like you saw on the sample. Okay this was my concern. My teacher told me not to answer parts F through H ... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
My teacher told me not to answer parts F through H because it deals with acids and bases. While units eight and nine are not going to be tested on the 2020 exam for AP chemistry, there definitely is acid-base chemistry and impurities. So I'm going to be using the chemistry and information about the technique known as t... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
No you are not going to see a pH curve like this but you should definitely be familiar with titration as a technique and stoichiometry as it applies to this situation. So here is a molarity calculation which is based on the volume of sodium hydroxide that was used in this experiment to titrate a 20 milliliter sample of... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
Now 0.300 capital M that means 0.300 moles of sodium hydroxide per one liter. I have written this conversion factor as a thousand milliliters so I can get my milliliters to cancel out. As you can see in the stoichiometry there is a one-to-one mole ratio between the acid and the base and that number 16.67 times 0.3 divi... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
That is not the final answer that is the moles of acid present in a 20 milliliter sample so the molarity would be moles divided by liters so not 20 but 0.02 liters 0.005 divided by 0.02 is 0.25 so correct answer 0.25 that is what we are looking for. Okay so showing some work to get a molarity of the acid of 0.25. Here ... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
All right again they're not showing superscripts and subscripts but I can definitely see what they're doing and they got the answer of 0.25 so again you are welcome to type your answer you don't have to show fancy handwritten dimensional analysis so typing is fine. This says molarity times volume equals molarity times ... | AP Chemistry Review of Timed AP Exam Practice #2_segment2.mp3 |
This phase change of solid water to liquid water is called melting, and it takes positive 6.01 kilojoules per one mole to melt ice. This change in enthalpy is symbolized by delta H with a subscript F-U-S, which stands for fusion. So this is called the heat of fusion. Next, let's think about the phase change of converti... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
Next, let's think about the phase change of converting liquid water into gaseous water. This phase change is called vaporization, and it also takes energy to convert liquid water into gaseous water. Specifically for water, it takes 40.7 kilojoules per one mole of liquid water to vaporize it. And so this change in energ... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
And so this change in energy is called the enthalpy of vaporization or simply the heat of vaporization. Let's go back and think about the structure of ice. Ice has water molecules in a repeating crystal structure, and the water molecules are held together by hydrogen bonds. So between these two water molecules here. Wh... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
So between these two water molecules here. When we add energy, we increase the freedom of motion. So over here is a picture of liquid water. So this is still held together by hydrogen bonds. These water molecules are still held together by hydrogen bonds, but we no longer have a crystal structure. So we have increased ... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
So this is still held together by hydrogen bonds. These water molecules are still held together by hydrogen bonds, but we no longer have a crystal structure. So we have increased freedom of motion. And it takes energy to disrupt that crystal structure. Next, let's think about converting liquid water into gaseous water ... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
And it takes energy to disrupt that crystal structure. Next, let's think about converting liquid water into gaseous water or steam. When water's in the gaseous state, there are no more intermolecular forces between the molecules. There's nothing holding them together. And so it takes a lot of energy to pull these two w... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
There's nothing holding them together. And so it takes a lot of energy to pull these two water molecules apart. It takes a lot of energy to overcome these hydrogen bonds. And that's the reason why we have such a large value for the heat of vaporization. So it takes a lot more energy to completely pull these molecules a... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
And that's the reason why we have such a large value for the heat of vaporization. So it takes a lot more energy to completely pull these molecules apart than it did to simply increase the freedom of motion. So 40.7 is a much bigger number than 6.01. If it takes positive 40.7 kilojoules per mole of energy to go from th... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
If it takes positive 40.7 kilojoules per mole of energy to go from the liquid state to the gaseous state, if we go in reverse from the gaseous state back to the liquid state, that same amount of energy is given off. So we can write 40.7 kilojoules per mole. However, since the energy is given off, we need to include a n... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
Going from the gaseous state to the liquid state is called condensation. So we could call this value of negative 40.7 kilojoules per mole the heat of condensation. And if it takes positive 6.01 kilojoules per mole to go from the solid state to the liquid state, if we go in reverse from the liquid state back to the soli... | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
And so we need to write in a negative sign here to indicate the energy is given off. When we go from a liquid to a solid, that's freezing. So this value is called the heat of freezing for water. | Enthalpy and phase changes Thermodynamics AP Chemistry Khan Academy.mp3 |
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