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Avogadro’s Principle. At equal temperatures and equal pressures, equal volumes of gases contain the same number of molecules. Dalton’s Law of Partial Pressure. The sum of the individual gas pressures equals the overall pressure of the mixture of gases. P 1 + P 2 + P 3 . . . = P total.
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Avogadro’s Principle At equal temperatures and equal pressures, equal volumes of gases contain the same number of molecules.
Dalton’s Law of Partial Pressure The sum of the individual gas pressures equals the overall pressure of the mixture of gases. P1 + P2 + P3 . . . = Ptotal
If a container has 116 torr H2, 109 torr CO2, and 176 torr O2, what is the total pressure of the mixture? 116 torr + 109 torr + 176 torr = 401 torr Our atmosphere is made of O2, N2 and other gases. If the atmospheric pressure is 760 mmHg and the pressure of N2 is 593 mmHg and the pressure of the “other” gasses is 8 mmHg, what is the partial pressure of oxygen? 760 torr – (593 + 8) = 159 torr O2
Gases are often collected using water displacement. The amount of water vapor in the collected gas mixture depends only on the temperature of the gas. H2O O2
52.5 ml of a gas is collected over water at 20˚C and 100.0 kPa. What is the pressure of the dry gas? 100.0 kPa = Pgas + Pwater Pwater at 20˚C = 2.3 kPa 100.0 kPa – 2.3 kPa = 97.7 kPa What would be the volume of this gas at STP? P1= 97.7 kPa P2=101.325kPa V1= 52.5 ml V2= ? T1= 20˚C=293 K T2=273 K
P1V1=P2V2 T1 T2 V2 = 47.2ml
