Avogadro's Principle “Equal volumes of gases at the same temperature and pressure contain equal numbers of particles” It doesn’t matter what type of gas you have (large or small), you will have the same amount of molecules in the same amount of space!

Example 1 You have a 2.0 L sphere filled with nitrogen gas. If the sphere is emptied, then filled with a mixture of oxygen and argon gases at the same temperature and pressure, how would the number of molecules compare? They would be the same!

Dalton’s Law Air is a homogeneous mixture Partial Pressure – contribution to pressure from each type of gas in a mixture The total pressure is equal to the sum of the partial pressures P total =P 1 + P 2 + P 3 + …. (for however many gases are present)

Example 2 A container holds argon, neon, and krypton gases. If the partial pressure of argon is 45 kPa, neon is 30 kPa, and krypton is 60 kPa, what is the total pressure of the container? P total =P 1 + P 2 +…. P total = P total = 135 kPa What is the percent composition of the mixture? Argon: 45/135 = 33.3% Neon: 30/135 = 22.2% Krypton: 60/135 = 44.4%

Example 3 Air is approximately 21% oxygen, 78% nitrogen, 0.9% argon, and 0.1% other gases. If atmospheric pressure is 101 kPa, what is the partial pressure of oxygen, nitrogen, and argon? Oxygen: 0.21(101) = kPa Nitrogen: 0.78(101) = kPa Argon: 0.009(101) = kPa

Example 4 A mixture of gases consists of 5 moles of oxygen, 14 moles of helium, 44 grams of carbon dioxide, and 2 moles of nitrogen. Calculate the partial pressure of each gas if the total pressure is 880 mm Hg. 44 grams CO 2 = 1 mole CO 2 Find total number of moles Use Proportions