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 reestablishing 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 going to 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 gases, what we call mostly noble gases.
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 at equilibrium, 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 got to 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 reactants that I just added or it can replenish the products that I've lost. So you're going to 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 aqueous, so it doesn't count. On the product side, I have one mole of gas and then another 4 moles of gas. 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 shifts 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 gases. Of course there can be other types of inert gas that exist, but for this level of chemistry, we're restricting into the noble gas. All right, so adding an inert gas can happen under two conditions other under constant volume or under constant pressure.
And for 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 going to say here partial pressures of gases are not changed. Now, if volume or pressure not mentioned, assume no shift. So let's say the question says you're adding 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 addition 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 shifts 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 reactants. So reactants will 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 inert gas. Now let's say you're adding a catalyst. Adding a catalyst does not cause a shift in equilibrium position, it simply changes the reaction rates. Remember, catalyst 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 reactants 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 then what I see here, so the outcome or explanation will 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.
