Chemistry Gas Laws - Video Tutorials & Practice Problems
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Chemistry Gas Laws are laws that relate together the pressure, volume and temperature of a gas.
Examining the Chemistry Gas Laws
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Chemistry Gas Laws
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The chemistry gas laws are laws that relate together the pressure, volume, and temperature of a gas. Now we're gonna say here that they can be derived from the ideal gas law. Remember, your ideal gas law is p v equals n r t. And to remember your 4 chemistry gas laws, just remember, be great at chemistry. The first chemistry gas law b is Boyle's law. Boyle's law looks at the relationship between volume and pressure. G stands for the Gay Lussac's law. It relates together pressure and temperature. A, a is for Avogadro's law. Avogadro's law looks at volume and moles. And then finally c, c stands for Charles law, which relates together volume and temperature. Now that we have chemistry gas laws connected to these pairings, let's take a look at the series of videos where we go in greater depths with each one of these chemistry gas laws.
The Ideal Gas Law can be used to determine each of the Chemistry Gas Laws
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Chemistry Gas Laws
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Boyle's law states that volume and pressure are inversely proportional at constant moles and temperature. Now, it's named after Robert Boyle and it illustrates how the volume of a container is greatly affected by pressure changes. Now, here how do we depict this relationship? When we say they're inversely proportional, we can say that they're on different levels. So we're gonna say volume is inversely proportional to 1 over oh, to inversely proportional pressure, which means that v, the proportionality symbol, 1 over p. This shows us our inverse relationship between volume and pressure. Think of it as volume being a numerator, pressure being a denominator. They're on different levels so they are different from one another. If one goes up the other one has to go down. Now, this is illustrated if we take a look at variables. Here if we take a look we have 2 containers with movable pistons. Volume is just the space within my container. So, if we look at this image we can say that the volume is pretty high. Pressure represents the downward force that we have on the piston. Now, the downward force on the piston must be pretty low which is why the piston hasn't slid down lower. Okay? And here we can see volume is high, pressure is low. Now, let's say that we garnered enough force from the pressure we're able to push down on this piston. We can see that the volume now is smaller, so the volume now is low and that's a direct result of the pressure being higher. Now, how do we depict this inverse relationship graphically? Well, here to show an inverse relationship between 2 variables you would show it like this. So this graph is showing me that my volume is decreasing over time and as a result the pressure is increasing over time. This is how we depict an inverse relationship between 2 variables. Now, how do we show Boyle's law formula in in the form of a digested formula? Here we'd say that it becomes p1v1 equalsp2v2. This represents our adjusted formula also our Boyle's law formula where p1 is our initial volume, v1 is our initial our p1 is our initial pressure, v1 is our initial volume, p2 is our final pressure, and v2 is our final volume. Now remember we went over how we derived these different types of formulas under the ideal gas laws application section. If you don't know what that is or if you haven't seen those videos yet, I suggest you go back and take a look at how we can derive this formula. Now we just know that it's connected to Boyle's law and therefore called the Boyle's law formula. Okay? So keep this in mind. Boyle's law says that pressure and volume are inversely proportional, meaning if one is high the other one would be low.
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Chemistry Gas Laws
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Now, Gay Lussac's law, also known as, Amatons law, says that pressure and temperature are directly proportional at constant moles n and volume v. Now, as temperature increases our gas particles collide with the walls more rapidly. That's because they're absorbing the thermal energy and they're using it to propel themselves faster inside the container. And this will cause an increase in my pressure. Now remember, pressure itself equals force over area. We said that the volume is constant, so your area would be constant, it's staying the same. If I'm increasing my temperature again my gas will move faster inside the container, They're gonna hit the walls more rapidly but also with more force. So my force is increasing, my area is staying the same, this causes my pressure to increase. Okay? So that's why pressure and temperature are directly proportional. Now, we're going to say remember that with all gas law calculations, we must use the SI units for temperature in Kelvin. So our units for temperature here are in Kelvin. Now, what is the pressure temperature relationship? They're directly proportional, so you just say that p is directly proportional to t, and that happens when moles and volume are the same or fixed, not the same but fixed. How do we show this? Well, here we have 2, images of pistons, containers with pistons that are movable. In the first image, I haven't applied a heat source, so we're going to say that our temperature here would be low. The temperature is low so our molecules don't have extra outside energy to absorb, so they're not moving as vigorously and as rapidly. They're not hitting the container with as much force, and therefore our pressure would be low. But all of a sudden I add a flame. The container absorbs the heat which eventually transitions to the molecules absorbing this heat allowing them to move more rapidly and with greater force. So temperature is high which eventually leads to greater force which leads to greater pressure. So pressure would be high. How would I depict this in a plot? They're both directly proportional so we'd say that they both would be increasing together so you'd have a line that's increasing over time. What would their adjusted formula be or the Gay Lussac's formula? It would just be P1 over T1 equals P2 over T2. Again, take a look at my ideal gas law applications section on how we could derive this formula. Now we know that it's connected to the Gay Louis Sacks or Amatons law. Now remember, with these variables we'd say initial pressure is p1, initial temperature is t1, final pressure will be p2, and final temperature will be t2. So, remember when we're talking about Gay Lussac's law or Amatons law that pressure and temperature are directly proportional when our moles, n, and our volume, v, are constant or fixed.
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Chemistry Gas Laws
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Avogadro's law states that our volume V and our moles n are directly proportional at constant pressure p and temperature t. Now, it's named after Amadeo, Avogadro and it shows that the volumes of gases are connected to their number of molecules. Here, we're going to say that the relationship between volume and moles is that V is directly proportional to moles, and again it happens when p and t are constant or fixed. The way we depict this with our mobile pistons is if we take a look here at this image, we're gonna say this container has a lot of dots, so it has a lot of moles or number of molecules. So moles would be high. To house all of these molecules we'd want our volume to be high, Because gases like it when there's an optimal amount of distance between them. But what happens if I take some of these molecules of gases out? Well, our moles of gas would be low, and I no longer need as much space for them so my volume would be low. They both are high together or low together when pressure and temperature are constant or fixed. Now, how do we depict this in a plot? Since they're directly proportional you'd say, this line of V and n would show it increasing over time. Where you could start out at 0 liters and it increases over time as our moles increase. Now, what would our adjusted formula or our Avogadro's Law formula be? That would just be v1 over n1 equals v2 over n2. So our initial variables here, initial moles would be n1 initial volume v1. Final moles would be n2 final volume would be v2. So just remember our volume and moles are directly proportional, meaning they're both high together or low together when our pressure and temperature are constant or fixed.
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Chemistry Gas Laws
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Charles law states that volume and temperature are directly proportional at constant moles n and pressure p. It's named after Jacques Charles and it illustrates how the volume of a container is greatly affected by volume. Here to show this direct proportionality between volume and temperature, we just say V is directly proportional to T when our moles and and pressure p are constant or fixed. If we were to illustrate this with movable pistons, if we take a look here we'd say that in this first image, our volume is low and we haven't applied any temperature or heat to this container, I mean, so the temperature would be low. Here I'm applying a flame to this. This is going to cause higher temperature. And what's happening here is because the piston is movable and the pressure is constant, our gas particles are gaining enough outside energy to basically hit all corners of this container including the movable piston up and that's what caused the volume to also expand. So our volume is high. How do we illustrate this direct proportionality between volume and temperature? Well, we'd say here that they're both increasing or decreasing together. So you can illustrate this by a line that's going up over time as they both increase. The adjusted formula or Charles' law formula would just become v1 over t1 equals v2 over t2. Here we'd say that our initial volume is v1, our initial temperature is t1, final volume is v2, and our final temperature is T2. So remember when it comes to Charles Long, we say that volume and temperature are directly proportional, which means they both can increase or decrease together if our moles n and our pressure p are held constant or fixed.
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Chemistry Gas Laws Example 1
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Here we're told that a 10 liter cylinder with a movable piston contains 10 grams of xenon gas. When an additional 10 grams of xenon gas are added, the volume increases. Which chemistry gas law can be used to justify this result? Alright. So within this question, what are we talking about? We're talking about the volume of a container, and they tell me when I add grams it increases. So they could be asking me to determine what the new volume is, so v 2. They're giving me 10 grams of a gas. If I know the grams of a gas, I can use that to find the moles of the gas. And then by adding additional grams of the gas that changes the moles. Right? So basically using this information it could help me find my second set of moles. So this question is really highlighting the fact that it's your volume and your moles that are changing. And based on the chemistry gas law that we know, we know that when we're dealing with volume and moles, it has to be Avogadro's law. So option b would be the correct choice. It is the only chemistry gas law that's talking about changes between volume and moles.
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Problem
Problem
A 10.0 L cylinder with a movable piston exerts 3.00 atm of pressure. What will happen to the pressure if the volume of the container increases to 20.0 L?
a) It will double
b) It will decrease by half
c) It will increase slightly
d) No change
A
It will double
B
It will decrease by half
C
It will increase slightly
D
No change
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Problem
Problem
A sealed container with a movable piston contains a gas with a pressure of 1380 torr, a volume of 820 mL and a temperature of 31°C. What would the volume be if the new pressure is now 2.83 atm, while the temperature decreased to 25°C?
A
0.0253 L
B
0.167 L
C
0.326 L
D
0.516 L
E
1.46 L
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