Chemistry Study Notes - Dalton's Law and Graham's Law

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Dalton’s Law ~ the partial pressure of each gas in a mixture of gases is proportional to the proportion of moles that the gas represents in the mixture.

Ptotal = P1 + P2 + P3…Composition of Dry AirPercentagePartial Pressure (kPa)N278.1 %79.11O221% 21.22Ar + others0.93% 0.95CO2 0.04% 0.04100%101.3 kPa (room pressure)Graham’s Law: At the same temperature, smaller particles (meaning lighter particles) have higher speeds V1/V2 = square root of (m2)/(m1)(m1)KE = ½ mv2The kinetic energy of gases depends on their speed and velocity. Two gases that are at the same temperature will have the same average Kinetic Energy. If the two gases have different masses, their speeds must also bee different. Which will have a higher speed? the lighter gasA gas’ particles move four times faster than oxygen’s at any temperature. Identify that gas from its molar mass.

V2 = 4V1V1 = ?V2/V1 = square root of (m2)/(m1)4V1/V1 = square root of (32)/(m2)16 = 32/m2m2 = 32/16 = 2Mystery gas is Hydrogen.

We can tell this because of its unique molar mass.

What is the partial pressure of water vapor in an air sample when the total pressure is 1.00 atm, the partial pressure of nitrogen is 0.79 atm, the partial pressure of oxygen is 0.20 atm, and the partial pressure of all other gases in air is 0.0044 atm?Ptotal = Pwater + Pall other gasesPwater = Ptotal – Pall other gasesPwater = 1.00 atm – (0.20 atm + 0.79 atm + 0.0044 atm)Pwater = 0.01 atmFind the partial pressure of oxygen in a sealed vessel that has a total pressure of 2.6 atm and also contains carbon dioxide at 1.3 atm and helium at 0.22 atm.

Ptotal = Poxygen + Pcarbon dioxide + PheliumPoxygen = Ptotal – (Pcarbon dioxide + Phelium)Poxygen = 2.6 atm – (1.3 atm...