Last Unit of Chemistry! (not the last lecture, but hey it’s something)

The Gas Laws Boyle’s law - pressure of a fixed amount of gas at a constant temperature is inversely proportional to the volume of the gas. (volume goes up, pressure goes down) at constant temperature P1V1 = P2V2

The Gas Laws Charles’s Law - the volume of a gas maintained at constant pressure is directly proportional to the absolute temperature of the gas. (at constant pressure)

Gay Lussac’s Law – the pressure exerted by a gas is directly related to the temperature when moles and volume are held constant.

The Gas Laws Avogadro’s law - the volume of a sample of gas is directly proportional to the number of moles in the sample at constant temperature and pressure.

The Gas Laws The combined gas law can be used to solve problems where any or all of the variables changes.

PVnRT4LYFE! The ideal gas equation (below) describes the relationship among the four variables P, V, n, and T. PV = nRT An ideal gas is a hypothetical sample of gas whose pressure-volume-temperature behavior is predicted accurately by the ideal gas equation.

The Ideal Gas Equation The gas constant (R) is the proportionality constant and its value and units depend on the units in which P and V are expressed. PV = nRT

The Ideal Gas Equation Standard Temperature and Pressure (STP) are a special set of conditions where: Pressure is 1 atm = 101.325 kpa = 760 mmHg = 760 Torr Temperature is 0°C (273.15 K) When converting from one unit of pressure to another, use the numbers above and factor label method. 101.325 kpa 760 mmHg 760 Torr 1 atm 1 atm 1atm

Pressure units 5.34 atm to mmHg 97.3 kpa to Torr 5.34 atm x 760 mmHg = 4058.4 mmHg 1 atm 97.3 kpa to Torr 97.3 kpa x 1 atm x 760 Torr = 101.325 kpa 1 atm

Dalton’s law of partial pressure - the total pressure exerted by a gas mixture is the sum of the partial pressures exerted by each component of the mixture:

Dalton’s law Not an equation like the rest of them, but more of a concept Works because we are saying that all gasses, regardless of kind, behave the same and therefor all take up the same space. Therefore, if a pressure is made of 10 moles of ten gasses, each one exerts 1/10th of the total pressure. If 5.4 atm is made up of 2 moles of fluorine gas, and 3 moles of chlorine gas, how much pressure do each exert?

Gas Mixtures Determine the partial pressures and the total pressure in a 2.50-L vessel containing the following mixture of gases at 15.8°C: 0.0194 mol He, 0.0411 mol H2, and 0.169 mol Ne. Solution: Step 1: Since each gas behaves independently, calculate the partial pressure of each using the ideal gas equation:

Gas Mixtures Determine the partial pressures and the total pressure in a 2.50-L vessel containing the following mixture of gases at 15.8°C: 0.0194 mol He, 0.0411 mol H2, and 0.169 mol Ne. Solution: Step 2: Use the equation below to calculate total pressure. Ptotal = 0.184 atm + 0.390 atm + 1.60 atm = 2.17 atm