1. Ideal Gases

2. Ideal Gas Law
The combined gas law assumes that the amount of gas does not vary.
You cannot use the combined gas law to calculate the number of moles of a gas in a fixed volume at a known temperature and pressure.

3. Ideal Gas Law
To calculate the number of moles of a contained gas requires an expression that contains the variable n.

4. Ideal Gas Law
The ideal gas law includes all four variables needed to calculate:
Pressure
Volume
Temperature
moles

5. Ideal Gas Law The ideal gas law is: PV = nRT
With R being the ideal gas constant at 8.31 (L∙kPa)/(K∙mol)

6. Ideal Gas Law Practice
A deep underground cavern contains 2.24 x 106 L of methane gas at a pressure of 1.50 x 103 kPa and a temperature of 315 K. How many moles of methane does the cavern contain?
Step 1: rearrange the Ideal Gas Law to isolate n. n = (PV)/(RT)

7. Ideal Gas Law Practice Step 2: Plug and Chug
n = (1.50 x 103 kPa x 2.24 x 106 L ) / (8.31 x 315K)
n = 128 mol methane

8. Ideal Gas Law Practice
9. When the temperature of a rigid hollow sphere containing 685 L of helium gas is held at 621 K, the pressure of the gas is 1890kPa. How many moles of helium does the sphere contain?

9. Ideal Gas Law Practice
10. A child’s lungs can hold 2.2 L. How many grams of air do her lungs hold at a pressure of 102 kPa and a body temperature of 37°C? (Hint: Find moles and then convert into grams using airs molar mass of 29g)

10. Ideal Gases and Real Gases
An ideal gas is one that follows the gas laws at all conditions of pressure and temperature.
At many conditions of temperature and pressure, real gases behave very much like an ideal gas.

11. Ideal Gases and Real Gases
Real gases differ most from an ideal gas at low temperatures and high pressures.