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Wake-up. How do you determine which gas constant to use in a ideal gas problem? 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.
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Wake-up • How do you determine which gas constant to use in a ideal gas problem? • 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?
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
Example #1 If 3 moles of N2 and 4 moles of O2are 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 = ? kPa V = 35 L n = 4 mol R = 8.314 L kPa mol K T = 25°C 298 K P = ? kPa V = 35 L n = 3 mol R = 8.314 L kPa mol K T = 25°C 298 K 212.36 + 283.15 495.51 kPa (x)(35) = (3)(8.314)(298) 35x= 7432.716 n= 212.36 kPa (x)(35) = (4)(8.314)(298) 35x= 9910.288 n= 283.15 kPa
Example #1 How 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 L n = ? R = 62.4 L mmHg mol K T = 26°C 299 K (625)(0.75) = (n)(62.4)(299) 468.75 = (18657.6)(n) N = 0.025 mol