UTF-8Gas LawSimulating an Ideal Gas:
I. State the Ideal Gas Law: give the value and of R in L x mmHg/(K x mol), and the SI units of the variables that describe the Ideal Gas Law.
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II. Gases have no definite shape or volume; they expand to fill the container. Explain this physical property in terms of the kinetic molecular theory (KMT).
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III. Based on the KMT predict the change (if any) in the temperature when the average speed of the particles decrease.
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IV. Which of the postulates of KMT are most nearly correct for all gases?
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V. Which of the postulates of KMT are violated to some extent by a real gases?
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We know that PV = nRT cannot be true because it implies that at T= 0 the molecules have zero volume! Real molecules have a volume, but usually in a gas this volume is very small compared to the volume they fill.
Another assumption is that the molecules do not attract each other -- so that at low temperature they do not form liquids or solids.
Avogadro proposed that equal numbers of gas particles at the same pressure and temperature should occupy the same volume.
In making this statement he was assuming the gas was behaving ideally which means it obeys PERFECTLY PV = nRT. He was also saying that it does not matter what the MASSES of the gases are.
So let's set up a simulation to test this.
1. Make the molecules in each container as small as possible, on both sides. (drop #1 atoms which will represent small molecules)
2. Adjust the intermolecular potential of the molecules on each side so that there are NO attractive forces. (set eV =0; no interactions)
3. Adjust the masses of the particles on the left have molecular weight = 32 grams/mole.
4. Adjust the masses of the particles on the right so they have molecular weight = 8 grams/mole.
The pressure is the same in each cylinder because the piston in each case has the same mass. (Piston is represented by the barrier, obstacle; to insert the obstacle into container click insert obstacle from additional tools. Click on the obstacle to set the size and parameters; set density at 0.1, vertical force at 0.1; adjust hight and width to be the same)
The temperature is also the same (4000 K) in each cylinder (see the thermometer). We adjust it with the menu item Heat Bath under Options --> Tools --> Heat Bath
Each container has the same number of particles (25).
Question: Does each container have the same number of moles of gas?
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VI. Build and perform the simulation (insert two Model Containers side-by-side)
1) Insert---Model Container---Basic 2D Molecular Simulator
2) Make all tools available to the Model Container (Tools---Add All Tools)
3) Add a #1 atom. Select the Pointer tool and then double click the atom to change its properties.
VII. Describe your observations here: Does the mass of the molecules affect the gas law?
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VIII. We know that for real gases the PV = nRT cannot be true because it implies that at T= 0 the molecules have zero volume! Real molecules have a volume, but usually in a gas this volume is very small compared to the volume they fill.
Additionally, for real gases there is the attraction between the molecules (intermolecular forces), so that at low temperature and high pressure they form liquids or solids.
IX. Build and perform the simulations.
1) Adjust the masses of molecules in both containers to be the same: 80 g/mole
2) Increase the size of molecules in the left container to 2A and set the intermolecular attractions (eV) at 0.2(double click on the molecule to set molecular mass, click enter; ckick change to set the size and eV; point to the curve and drug to the radius=2, enter)
3) Increase the size of molecules in the right container to 2A and set the intermolecular attractions (eV) to 0.4
{Your observation:
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truetrue0 255 0true0 255 00 255 0true0 255 00 255 00 255 0true0 255 00 255 0true0 255 00 255 00 255 0true0 255 00 255 00 255 0truetrue255 0 2550 255 00 255 0trueorg.concord.mw2d.activity.AtomContainerGas Law$0.mmlorg.concord.mw2d.activity.AtomContainerGas Law$1.mmltrue0 255 00 255 00 255 0truetrue0 255 00 255 00 255 00 255 0