Chemistry Practice Problems Van der Waals Equation Practice Problems Solution: The graph below shows the change in pressure as th...

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Solution: The graph below shows the change in pressure as the temperature increases for a 1 mol sample of a gas confined to a 1 L container. The four plots correspond to an ideal gas and three real gases: CO2, N2, and Cl2.At room temperature, all three real gases have a pressure less than the ideal gas. Which van der Waals constant, a or b, accounts for the influence intermolecular forces have in lowering the pressure of a real gas?

Problem

The graph below shows the change in pressure as the temperature increases for a 1 mol sample of a gas confined to a 1 L container. The four plots correspond to an ideal gas and three real gases: CO2, N2, and Cl2.
A graph of pressure versus temperature shows that gas B and an ideal gas follow nearly the same trend while gases A and C are parallel but lower pressure at the same temperatures. The x-axis is temperature in Kelvin, ranging from 250 to 550 with intervals of 50. The y-axis is pressure in atmospheres, ranging from 15 to 45 with intervals of 5.

At room temperature, all three real gases have a pressure less than the ideal gas. Which van der Waals constant, a or b, accounts for the influence intermolecular forces have in lowering the pressure of a real gas?

Solution

The Van der Waals' Equation is as follows:

where a is the polarity coefficient, which accounts for the attractive or repulsive interactions of the gas molecules, and b is the size coefficient, which accounts for the size of the individual gas molecules. This equation show how real gases deviate from ideal behavior.

We can rearrange this equation to see how both a and b affect the pressure of the gas.

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