Wake-up

1. How do you determine which gas constant to use in a ideal gas problem?

2. How many moles of air are there in a 125 mL Erlenmeyer flask if the pressure is 755 mm Hg and the temperature is 20°C?

What gases make up the atmosphere?

Gases in the Atmosphere

Dalton’s Law of Partial Pressure

Total pressure exerted by a mixture of gases is equal to the sum of the partial pressure of the

gases in the mixture

Partial Pressure

Pressure which the gas would have if it alone in the volume

Dalton’s Law Formula

See Reference Table

Dalton’s Law

Example #1If 3 moles of N2 and 4 moles of O2 are placed in a 35 L

container at a temperature of 250 C, what will the pressure (kPa) of the resulting mixture of gases be?

P = ? kPaV = 35 L

n = 3 molR = 8.314 L kPa mol KT = 25°C 298 K

(x)(35) = (4)(8.314)(298)35x = 9910.288n = 283.15 kPa

P = ? kPaV = 35 L

n = 4 molR = 8.314 L kPa mol KT = 25°C 298 K

(x)(35) = (3)(8.314)(298)35x = 7432.716n = 212.36 kPa

212.36 + 283.15495.51 kPa

Example #1How many moles of N2 are in a 750 mL vessel at

26 degrees Celsius and 625 mm Hg?P = 625 mmHg

V = 750mL 0.750 Ln = ?

R = 62.4 L mmHg mol KT = 26°C 299 K

(625)(0.75) = (n)(62.4)(299)468.75 = (18657.6)(n)

N = 0.025 mol