Effusion is the escaping of gas molecules or atoms through a pinhole.
Effusion
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concept
Effusion
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So when it comes to the state of matter in terms of gases, realize that a gas that exists by itself in fact it's a collection of molecules or atoms that are in constant motion. And we're going to say with this collection of gaseous molecules or atoms there's some terms that you need to keep in mind. We have mean free path, effusion versus diffusion. Now, mean free path, this is just the average distance traveled by gas molecules between their collisions. Remember, gas molecules are very far apart and spread apart within a container. But they do come into contact with one another because they're bouncing around, they're going to interact. Now, a mean free path is just the distance between 2 gas particles before they collide. When it comes to effusion and diffusion there are some differences. Now, here we have images for effusion versus diffusion. For a fusion, this is just the escape of gaseous molecules or gas molecules or atoms through a pinhole, So the opening is very small. Because this opening is very small, that means these gases typically exit the container in a one by one fashion. K. It's not all of them coming out at once, it's 1 by 1. For diffusion though, diffusion is just the motion of a gas mixture gas molecules may not The gas molecules may not necessarily try to leave the container. Remember, they're going from an area of high concentration to an area of low concentration. If inside is high concentration then the gas molecules will escape to go outside. But if outside is higher concentration then some gas could actually go into the container. So that's a big difference from a fusion. In a fusion you're only going out. For diffusion it's all based on concentration. You're always going to the area that has lower concentration, whether that's inside or outside the container. Secondly, for diffusion the opening is bigger and because this opening is bigger more than one gas molecule can exit at a time or enter at a time. Okay? So those are the subtle differences between effusion and diffusion. Remember, a gas particle doesn't exist by itself. It's a collection of gases. There are other gases around the vicinity. Okay? So keep this in mind when talking about the behavior of any particular gas that you may read about.
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concept
Effusion
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The rate of a fusion states that the rate of a gas is inversely proportional to the square of their mass. So that means rate of gas equals 1 over square root of molar mass. But what exactly does that mean? Well, in simple terms, it means increasing the molar mass of a gas means that we are going to lower its speed and the lower its rate. So basically the more a gas particle or molecule weighs, then the slower it's going to move. So that's basically the idea behind the rate of a fusion.
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example
Effusion Example 1
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Here it says to rank the following in order of increasing rate of effusion. Remember, we said that the higher the molar mass then the lower the speed or rate of a gas. So here if we take a look, o 2 has 2 oxygens, the combined mass would be 32 grams per mole. P f 5 has 1 phosphorus and 5 fluorines. When you add them all up together, it gives you approximately a 125.97 grams per mole. Carbon dioxide weighs approximately 44.01 grams per mole, when you add up the 1 carbon and the 2 oxygens. And then xenon, if you look on the periodic table, it has a weight of approximately a 131.29 grams per mole. We wanna do it in terms of increasing rate of effusion, which means we're going to start out with the heaviest which has the slowest rate, all the way up to the lightest one which has the highest rate. Alright. So who has the highest molar mass or highest weight? It would be xenon. Xenon will be the slowest and therefore lowest rate of effusion. Then we have p f 5, then we have c0 2, and then o 2 weighs the least out of everyone, so it would move the fastest. So this would be our order going from the slowest rate of effusion to the highest rate of effusion based on their individual molar masses.
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concept
Effusion
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Now, Grand's lava fusion is used when comparing the rate of 2 different non reacting gases. And we're going to say here that the effusion rate of a gas and its time to travel are directly proportional. So let's say that we're dealing with gases a and b. So gas a and gas b. Since rate and time are directly proportional, that means they'll be on the same level. So the rate of gas a is equal to the time of gas a. The rate of gas b is equal to the time of gas b. But then remember, when we talked about the rate of effusion, the effusion rate of a gas and its molar mass are inversely proportional. So that would mean that the rate of gas a is on top therefore, the molar mass of gas a would have to be on the bottom, then the rate of gas b is here on the bottom, and therefore, its molar mass has to be here on top. So remember, when when we're directly proportional we're on the same level with one another, and when we're inversely proportional, one will be numerator and the other will be the denominator. Understanding these relationships are key to answering questions dealing with Graham's law of effusion.
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example
Effusion Example 2
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Here the example question says, calculate the ratio of the infusion rates of helium to methane. Alright. So the first gas that's name represents our gas a, and the second one will represent our gas b. So here we're going to say rate of helium divided by the rate of methane. We don't we're not given times for them so we can't use time in terms of this question, but we know the identity of the gases. Therefore we know their molar masses. So this equals remember, rate and molar mass are inversely proportional. So if the rate of helium is on the top, then the molar mass of helium has to be on the bottom. Because the rate of methane is on the bottom, the molar mass of methane has to be on top. Here we have 1 carbon and 4 hydrogens. When you add all of their masses together from the periodic table, we'll get its mass as 16 0.04 2 grams per mole for methane. When you look up the atomic mass of helium on the periodic table, it's 4.003 grams per mole for helium. So divide 16.04 2 by 4.003 and take the square root, and that gives us approximately 2.00187. So this would be the ratio in terms of the rate of effusions for helium to methane. Now what is this number telling us? Well, what this number is telling us, it's telling us that helium moves twice as fast as methane. And this makes sense because helium weighs less. Remember, we said that the less you weigh, the faster you're going to be able to move as a gas. Because methane weighs more, it makes sense it's not gonna be able to move quite as fast as helium. So again, when we're figuring out the rate of gas a to gas b, whatever is discussed first is gas a, second one is gas b. The answer is telling us how much faster the top gas, in this case, helium, is to methane.
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Problem
Problem
If H2 has an effusion rate that is 3.72 times faster than a gas, what is the identity of the unknown gas?
A
Cl2
B
CO2
C
N2O4
D
N2
E
O2
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Problem
Problem
How many times faster will H2 gas pass through a pinhole into an area of vacuum than O2 gas?
A
32
B
2
C
2.5
D
4
E
8
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Problem
Problem
It takes 6.3 minutes for 2.3 L argon to effuse through a semipermeable membrane. How long would it take for 2.3 L of chlorine gas to effuse under similar conditions?