QuickNotes
Real Gases
- The theory assumes that as pressure increases, the volume
of a gas becomes very small and approaches zero.
- Intermolecular forces do exist in gases. These become
increasingly important in low temperatures, when molecular motion slows
down, almost to a halt.
- Real
gases behave ideally only at high temperatures and low
pressures
- Understanding how the ideal gas equation must be
modified to account for real gas behavior helps us understand how
gases behave on a molecular level.
***Read section 5.9 in your Zumdahl textbook to get an in depth analysis of the characteristics of real gases.
Van der Waals Equation
- Van der Waals found that to describe real gas behavior we must consider particle interaction and particle volumes.
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| The values for a and b are given in table 5.3 of the Zumdahl textbook. |
Carbon dioxide gas (1.00 mole) at 373 K occupies 536 mL at 50.0 atmosphere pressure. What is the calculated value of the pressure using:
(i) Ideal gas equation
(ii) Van der Waals equation?
Given Data:
Van der Waals constants for carbon dioxide: a = 3.61 L2 atm mol-2 and b = 0.0428 L mol-1
Van der Waals constants for carbon dioxide: a = 3.61 L2 atm mol-2 and b = 0.0428 L mol-1
Solution:
R = 0.0821 L atm K-1 mol-1.
(i) Using the Ideal Gas Equation:
V = 0.536 L
n = 1.00 mol
T = 373 K
PV = nRT
P = nRT/V = 1.00 x 0.0821 x 373/0.536
= 57.1 atm
(P + an2/V2)(V - nb) = nRT.
(P + 3.61 x (1.00/0.536)2)(0.536 - 1.00 x 0.0428) = 1.00 x 0.0821 x 373)
(P + 12.57)(0.493) = 30.62
P + 12.57 = 62.12
P = 49.6 atm
To make sure you totally understand Real Gases, check out this review video!
Are you ready? Get out a calculator and take a mini-quiz. If you get a 100%, move onto the next concept! (Make sure you have an additional tab open to play at kahoot.it. You will need to keep 2 tabs open to play and view the questions.)
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