Start typing, then use the up and down arrows to select an option from the list. ## General Chemistry

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7. Gases

The Van der Waals Equation is used when dealing with real, non-ideal gases.

Understanding the Van der Waals Equation
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concept

## Van der Waals Equation 1m
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the Vander Waals equation is an equation used for real gas is it combines the effects of attractive forces and gas volume to describe non ideal behavior. So the behavior of real gasses, we're gonna say deviations from this ideal gas behavior happens at high pressures and low temperatures. Remember, an ideal gas is imaginary, and ideal gasses behave as though they are alone. This is not possible if the pressure is incredibly high inside the container. At high pressures, it forces gas molecules to come closer together so they can't be alone and at lower temperatures that also causes gas is to start to condense downward. This also forces them to becoming closer contact with one another. Now, with the Vander Waals equation, we have two coefficients, which we call variables or Vander Waals constants. The polarity coefficient is the Vandals constant with the letter A and it corrects for the attractive forces felt between gas molecules, the size coefficient, it is the Vander Wal's constant be that corrects the volume of gas molecules. Now with the Vander Wal's constant be. What we need to realize is, as we increase the molecular weight of a gas, then this causes an increase for this Vander Wal's constant. So the greater the molecular weight of a gas, the greater its Vander Wal constant be now that we've seen the whole idea of these coefficients, and we know that the Vander Waals equation is used for real gasses, click on the next video and let's take a look at the formula involved.
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concept

## Van der Waals Equation 3m
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example

## Van der Waals Equation Example 1 3m
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here. The example Question states using the Vander Waals equation determine the pressure of g oxygen gas in 250 ml graduated flask when the temperature is 50 degrees Celsius. Alright, So we're going to say the Vander Waals equation is pressure plus n squared times, a over V squared times volume minus end times B equals and are cheap. Now all we gotta do is plug in the values that we have. So we need to have the moles off oxygen. Remember, oxygen is diatonic. So one mole of 02 ways 32 g, though, too. So when we do that, we're gonna get our moles of 02 comes out as 20.6 to 5 moles of 02 volume has to be in leader. So that's 0.250 leaders and then temperature needs to be in Kelvin. So at 2 73 15, that gives us 3 23 points. 15 Kelvin. Since we're dealing with 02 in the charts up above, we would see that the a constant it comes out to 1. The B constant comes out 2. with this information, we plug it into the formula. All right, so let's see, we're looking for pressure, so we don't know it. So this is gonna be 0.6 to 5 squared times 1.360 divided by volume squared, which is 0.250 squared. And this is gonna be times volume, which is 0.250 minus moles, which is 0.6 to 5 times 0.318 And this is gonna equal. My moles are and t so, moles we wanna actually move all this out of the way. So we have space to write this out. So here are moles again. Come out to 0.6 to 5. So the Vander Waals equation related to the ideal gas law so are again is 0.8 to 06 and then temperatures 23 15 Kelvin, When I multiply these three together on this side, it comes out to be see, we're gonna multiply those out together. That comes out to be 16. 356 When I when I do this value minus these two multiplying, what I get is I'm going to get 0. Then when I work all of this out in here, this comes out to be 8. plus p. So now I need to isolate my P. So I'm gonna divide both sides here by 0. So plea P plus eight five equals 72.0 Subtract 85 from both sides. So P equals 63. atmospheres. So that would be the pressure of 02 when utilizing the Vander Wal's equation.
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Problem

Which gaseous compound is expected to have the largest value for the Van der Waals constant b?

a) O2

b) CH3CH3

c) HBr

d) S8

e) Ne 