Ideal Gases Ideal Gas Law The combined gas

Ideal Gases

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.

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

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

Ideal Gas Law • The ideal gas law is: o PV = n. RT o With R being the ideal gas constant at 8. 31 (L∙k. Pa)/(K∙mol)

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 k. Pa 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)

Ideal Gas Law Practice • Step 2: Plug and Chug – n = (1. 50 x 103 k. Pa x 2. 24 x 106 L ) / (8. 31 x 315 K) – n = 128 mol methane

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 1890 k. Pa. How many moles of helium does the sphere contain?

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 k. Pa and a body temperature of 37°C? (Hint: Find moles and then convert into grams using airs molar mass of 29 g)

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.

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