Le Chatelier's Principle - Video Tutorials & Practice Problems
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1
concept
Understanding Le Chatelier's Principle
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7m
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Now, le Chatelier's principle says that if a chemical reaction is at equilibrium and it's disturbed, it adjusts itself by shifting in a certain direction. Now, the direction of the shift depends on minimizing or canceling the disturbance and reestablished equilibrium. Remember a chemical reaction in these cases wants to be at equilibrium. So it's just moving to the left or to the right in order to re obtain that equilibrium status. Now we're gonna say here that the following disturbances are carried out at constant temperature later on, we'll talk about what if temperature is changing, what effect would that have? But for now, let's focus on the factors that have nothing to do with temperature. So here we're talking about the disturbances of chemical equilibrium. So we're looking at different factors. We're talking about changing the concentrations of your gaseous or aqueous compounds, adjusting pressure or volume. And then the introduction of inert gasses, what we call most, mostly noble gasses. We'll talk about the type of changes, are we increasing or decreasing these effects? We'll look at an example of a chemical reaction and then we'll explain what's going on. All right. So first, let's talk about concentrations of gaseous and aqueous compounds. So here, let's say that I want to increase my reactants. Now realizing here that if you're increasing reactants, what's the opposite of that decreasing products? Ok. So whether you're increasing reactants or decreasing products, the same effect will happen. So think of it as a balancing act, let's say that I have added additional reactants to my chemical reaction. It was a rated equilibrium, it was fine. But then I decided to add more reactants. I got to remove that excess reactants that I've just added. I can't physically take my hand and dunk it into the solution because maybe it's dissolved in there. So what is the course of action that needs to be taken by the chemical reaction? Well, if I put reactants, I gotta move in the forward direction to get rid of it, moving in the forward direction will convert those excess reactant molecules into products. In another way, let's say I decrease my products. OK. I've just depleted my products. How do I make more? Again, we would move in the forward direction, moving in the forward direction towards my products would cause an increase in the amount of products. So here we're going to say the arrow moves this way. OK. So moving this way can cause a decrease in the amount of reactant that I just added or it can replenish the products that I've lost. So you're gonna have more products will be made next pressure and volume. If you looked at my videos dealing with the gas laws, we know that pressure and volume have an inverse relationship if pressure goes up, volume goes down. So let's say that I'm increasing pressure. If you're increasing pressure, that's equivalent to saying that I'm decreasing volume. Here, we're going to say we have to look at the gaseous compounds on both sides of the arrow to understand which way it will shift on the reactant side. Here's a gas and I have two moles of it. This is a que so it doesn't count on the product side. I have one mole of gas and then another four moles of gas. So that's five moles of gas total. If I increase my pressure or if I decrease my volume, then my reaction shifts to the side with less moles of gas. So here it would shift this way, it would shift towards the reactants because the reactant side has less moles of gas. Next, we have inert gas. Now, when I say inert gas, we generally are talking about your noble gasses. Of course, there can be other types of inert gasses that exist. But for this level of chemistry, we're restricting it to the noble gasses. All right. So adding an inert gas can happen under two conditions either under constant volume or under constant pressure if we're adding an inert gas under constant volume. So here it will cause no shift the inert gas we're adding is neon gas. We're gonna say here, partial pressures of gasses are not changed. Now, if vine or pressure not mentioned as soon, no shift. So let's say the question says you're adding um some nitric neon gas to your chemical reaction. They don't mention that it's under constant volume or constant pressure. You just assume that it's being done under constant volume and no shift, no reaction will take place. Now, if we're adding under constant pressure, what effect happens? Well, if you're adding under constant pressure, then something can happen again. Remember this side has two moles of gas total. And this side here has five. If you're adding an inert gas under constant pressure, realize that the the addition of an of of more gas into your reaction means that the volume has to expand in order to accommodate it. So your volume would increase and this causes a shift to the side with more moles of gas. In this example, the product side has more moles of gas. So it shift to the right now. These are things that we need to remember also remember that the side that you're shifting to wherever you're shifting to will be increasing in amount. And if you're increasing in that direction, the other side will be decreasing in amount. So here we're shifting towards reactant. So reactants would be increasing in amount and this ought to be decreasing in amount. If there's no shift, there's no increasing or decreasing on either side. Again, here we're shifting towards the product side. So the product side would be increasing in amount and this ought to be decreasing in amount. Ok. So keep in mind, these are the different changes that you can do playing around with the concentrations of gaseous or aqueous compounds playing around with your volume or pressure or the introduction of an earth gas. Now, let's say you're adding a catalyst, adding a cyst does not cause a shift in equilibrium position. It simply changes the reaction rates. Remember, a cyst lowers your energy of activation, thereby speeding up the reaction. It has no control of which way your reaction will shift to the left or to the right. OK. So here recall these different changes that we can do and remember if this is true under these conditions, if you reverse them, then the reverse would be true. Meaning that if I decrease my reactant amounts or I increase my product amounts, then we would have more reactants being formed. If I decreased my pressure or increased my volume, then I'd shift to the side with more moles of gas. OK. Here I didn't put the other scenario, just memorize this version here. You see it, you have the rule for it. If you're seeing the opposite on your test, then just remember the conditions have been flipped than, than what I see here. So the outcome or explanation would be flipped. OK? So keep this in mind, when looking at Le Chatelier's principle and the different types of changes that can take effect.
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example
Le Chatelier's Principle Example
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2m
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Here it says consider endothermic reaction at equilibrium. So here this chemical reaction is endothermic. It says predicted the reaction will shift to the right left or no shift after each disturbance. All right. So for the first one, it says we're removing some 02. If we look at our equation 02 is a product. Think about keeping things balanced. You wanna maintain your equilibrium status. I've just removed some product from my chemical reaction. I need to make more. So which way would we need to shift in order to produce more product? We'd have to move in the forward direction or to the right next. I'm adding some glucose right here. I'm adding some product gotta maintain that equilibrium status. I gotta shift in order to re-establish it. How do I get rid of the product that I just added? I have to deplete it. So I have to move in the reverse direction, moving in the reverse direction will cause a decrease in the product because it's going to be converted into some reactant next volume of container decreased. So remember if your volume decreases, that's equivalent to the pressure increasing. Remember if volume is decreasing or pressure is increasing, we shift to the side with less moles of gas. So if we look, we have 12 moles of gas total on this reacted side. And then we have six moles of gas. Over here. On the product side, we're shifting to the side with less moles of gas. So we have to shift to the right. Finally, Xenon gas added to reaction mixture here, we're not told that it's under constant volume or constant pressure. So we're assuming it's being done under constant volume, under constant volume, there will be no shift because you have not disrupted your equilibrium status. Again, they'd have to explicitly say under constant pressure for you to take into account that the change has happened and what, which way do I need to go? All right. So just remember, keep reviewing those little chat principal um rules and you'll be able to answer questions like this that much easier.
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concept
Temperature Changes
Video duration:
3m
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Now let's take a look at the effect the temperature has on our equilibrium status based on the Shuffler's principle. Here, we're going to say changing the temperature of the reaction at equilibrium will disrupt the equilibrium and cause a shift. But how exactly does it work? Well, we're gonna have to say here that entropy which remembers delta H over reaction plays a big role in the direction of the change. Here, we're gonna say recall that the equilibrium constant is temperature dependent. So changing the temperature not only can affect which way we shift, but it can also affect the scale or value of your equilibrium constant K. So here, let's take a look, we have entropy type, we have the type of change that can occur, whether we're increasing or decreasing. We have examples and then we have explanations. So in the first row, we have the explanation that we're shifting away from heat. Now we shift away from heat if we're increasing the temperature. Now this is true, whether it's exothermic or endothermic, increasing, the temperature causes a shift away from the heat source. If we're talking about an exothermic process, delta H is negatively charged exothermic means we're releasing heat. So, heat has to be a product. All right. So we increase the temperature, we're gonna shift away from the heat, which means I'd have to move away from it. So I'm gonna move towards the reactant side. We're gonna go to the left and remember the direction you shift in that side would be increasing in amount. So our reactants would increase in amount and conversely, the, the products would be decreasing out. Because remember if one side is increasing, the other side has to be decreasing. Now, here for the second row, we're shifting towards the heat. Now this is true, whether it's endothermic or exothermic. If we decrease our overall temperature of the chemical reaction, the reaction have to shift towards the heat. So here if you're an endothermic process, your entropy is po your entropy is positive. If it's positive, you're absorbing heat. So heat has to be a reactant, we are decreasing our temperature. So we're gonna have to shift towards it. In this case, we're moving towards the left again towards the heat. So again, wherever you're moving to will be increasing in amount. If this side is increasing, the other side is decreasing. So when it comes to this idea of temperature, le chatelet principle, first, it's important to understand is your reaction endothermic or exothermic. This will tell you what side heat will be found. Once you've established a location of heat, then you look to see OK. Is my heat, is my temperature increasing or decreasing? If temperature is increasing, I shift away from the heat, if temperature is decreasing, I shift towards the heat. So keep that in mind, anytime you're dealing with a question that ties together temperature and Le Chatelier's principle.
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example
Le Chatelier's Principle Example
Video duration:
2m
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Here, it says consider the reaction, we have one mole of nitrogen gas reacting with one mole of oxygen gas and one mole of B roaming gas to produce two moles of nobr gas. Here, we're told the entropy value was negative 32.5 kilojoules. So here we're saying that the entropy is negative. So it's exothermic which means heat is re released. So heat would have to be a product. All right. So now the phone changes will shift equilibrium to the left except, all right. So removing and two, if you remove some reactor, you have to replenish the reacting you lost. So you would have to move in the left direction to remake it. So this does move to the left, increasing the partial pressure of Nobr. So when we say increase the partial pressure of a gas, that just means adding more moles of that gas because remember the quantity of a gas is directly connected to its partial pressure, the more of it that we have the higher the partial pressure. So in essence, this part C is saying that I'm increasing the amount of product to get rid of it. I'd have to move to the left again to get rid of it. So this is out in increase the pressure of container. Now, this is different. We're not increasing the partial pressures of any gasses. We're increasing the overall pressure of the container, increasing pressure is equivalent to decrease in volume. In either instance, all that means that we're shifting to the side with less moles gas on this side. Here, let's see this side. Here, we have three moles of gas on this side here we have two moles of gas. So again, we're shifting to the side that has less moles of gas. So we're shifting to the right. So right now, this is an example of a shift that's not to the left. Next, adding some NOBR is equivalent to option C where we're increasing the partial pressure of NOBR. They're both saying the same thing, we shift to the right um to the left to get rid of it, decreasing the temperature. If we're decreasing the temperature, we have to shift towards the heat. The heat is on the product side. So we'd be shifting towards the right. So this is also an example of the equilibrium shifting to the right and to the left, sorry to the right to the right. Now, lastly, f decrease the container volume, which is the same thing as saying E were decreasing container volume, which is the same thing as increasing pressure of the container. So we're gonna shift to the side with less moles of gas. So this would also shift to the right. So in this one, Ednf would all shift to the right. So they would be the answer. They're the ones that are not shifting to the left. Right. So again, de and F are our final answers.
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Problem
Problem
Select correct answer(s) that would yield more products in the following reaction.