DALTON’S LAW OF PARTIAL PRESSURES

DALTON’S LAW OF PARTIAL PRESSURE . In 1801, Dalton found out that the total pressure of a mixture of gases is equal to the sum of the partial pressure exerted by each gas. This is known as Dalton’s law of partial pressure. Each gas in the mixture exerts a pressure that is independent of the other gases present. These pressures are called partial pressures

DALTON’S LAW OF PARTIAL PRESSURE N2 + O2 N2 O2 Thus if we have a mixture of two gases, O2 = 0.1 atm N2 = 0.7 atm PTOTAL= 0.8 atm Mathematically this can be stated as: PTOTAL = P1 + P2 + P3 + …

DALTON’S LAW OF PARTIAL PRESSURE So the total pressure in the container is to some of the partial pressures of each component in the mix Dalton’s Law of Partial Pressure can be explained by 2 concepts from the Kinetic Molecular Theory. The pressure of a gas is caused by the collision of molecules with the walls of the container. Gas molecules act independently of each other.

DALTON’S LAW OF PARTIAL PRESSURE Mole fraction = Mole Fraction is a way of measuring the contribution of an individual gas within a mixture It is measure by number of moles of x divided by the total number of moles

DALTON’S LAW OF PARTIAL PRESSURE Mole fraction = Moles of x Total # of moles in the mixture Mole Fraction is a way of measuring the contribution of an individual gas within a mixture It is measure by number of moles of x divided by the total number of moles

DALTON’S LAW OF PARTIAL PRESSURE: APPLICATION TABLE 1: PARTIAL PRESSURE CHANGES DURING RESPIRATION GAS Partial Pressure (kPa) INHALED AIR EXHALED AIR N2 (g) 79.3 75.9 O2 (g) 21.3 15.5 CO2 (g) 0.040 3.7 H2O(g)* 0.67 6.2 * The quantity of water in air varies. The value used in this table is based on a relatively low humidity. Gas exchange between living organisms and the environment depends on the properties of gases, in particular, partial pressure and solubility. RESPIRATION is one of the most important processes because we need to breathe OXYGEN and breathe out CO2 in order to live. Oxygen is the most important gas in the atmosphere, it makes up 21 % of the volume of dry air. Partial pressure of a gas is more useful than percentage composition because it is the pressure of oxygen that determines how much oxygen is absorbed by the lungs of the person.

DALTON’S LAW OF PARTIAL PRESSURE: APPLICATION POXYGEN = 0.21 X 760 torr = 159.6 torr 21 % of the volume and pressure of the atmosphere is due to OXYGEN. The partial pressure of oxygen can be calculated by multiplying the percent in decimal form by the total pressure. We function best breathing this partial pressure of oxygen.