III. Ideal Gas Law and Dalton’s Law of Partial Pressure Gases

V n A. Avogadro’s Principle b Equal volumes of gases contain equal numbers of moles at constant temp & pressure true for any gas

PV T VnVn PV nT A. Ideal Gas Law = k UNIVERSAL GAS CONSTANT R= L  atm/mol  K R=8.315 dm 3  kPa/mol  K = R 1dm 3 = 1L Merge the Combined Gas Law with Avogadro’s Principle:

A. Ideal Gas Law UNIVERSAL GAS CONSTANT R= L  atm/mol  K R=8.315 dm 3  kPa/mol  K PV=nRT

GIVEN: P = ? atm n = mol T = 16°C = 289 K V = 3.25 L R = L  atm/mol  K WORK: PV = nRT P(3.25)=(0.412)(0.0821)(289) L mol L  atm/mol  K K P = 3.01 atm C. Ideal Gas Law Problems b Calculate the pressure in atmospheres of mol of He at 16°C & occupying 3.25 L.

GIVEN: V = ? n = 85 g T = 25°C = 298 K P = kPa R = dm 3  kPa/mol  K C. Ideal Gas Law Problems b Find the volume of 85 g of O 2 at 25°C and kPa. = 2.7 mol WORK: 85 g 1 mol = 2.7 mol g PV = nRT (104.5)V=(2.7) (8.315) (298) kPa mol dm 3  kPa/mol  K K V = 64 dm 3

Dalton’s Law of Partial Pressure Dalton’s Law of Partial Pressure The total pressure of a mixture of nonreacting gases is equal to the sum of the partial pressures of the individual gases (P total = P 1 + P 2 + P 3 + …)

Problem 1 b 1 L of N 2 at 50 kPa is mixed with 1 L of O 2 at 60 kPa, to form a 1 L mixture of the gases. What is the resulting pressure? What are the partial pressures? b Total pressure = 60 kPa + 50 kPa = 110 kPa

Problem 2 b A balloon contains 75 kPa N 2, 15 kPa O 2, 5 kPa CO 2, and water vapour. If atmospheric pressure is 100 kPa what is the partial pressure of water vapour? b ( ) = = 5 kPa