Page 1:

• Chemists often work with gas mixtures, such as air, which contains multiple gases.

• In this activity, we will learn how to calculate the pressure of a gas in a mixture.

• Model 1 shows three tanks with different gases.

• All three tanks have a volume of 10.00 L.

Page 2:

• Calculate the moles of oxygen gas and nitrogen gas for each tank in Model 1.

• Use the Ideal Gas Law to calculate the pressure of oxygen gas in Tank A.

• Use the Ideal Gas Law to calculate the pressure of nitrogen gas in Tank B.

• The total pressure in Tank C is the sum of the partial pressures of oxygen and nitrogen gases.

• The pressure of oxygen gas in Tank C is a partial pressure.

Page 3:

• Enter the partial pressure values for oxygen gas and nitrogen gas in Tank C of Model 1.

• The relationship between the partial pressures of oxygen gas and nitrogen gas and the total pressure is given by the equation P = Pn2 + PN2.

• Combining gases at constant temperature and volume increases the total pressure proportionally to the amount of gas added.

• A chemistry student adds a third gas, Gas Z, to Tank C in Model 1.

• Calculate the partial pressure of the component gases after the addition of Gas Z.

• Calculate the total pressure in the tank with all three gases present.

• A reaction in the tank consumes all of the oxygen gas, reducing the total pressure.

Page 4:

• A scuba tank contains a mixture of oxygen and helium gases.

• Calculate the total pressure in the scuba tank before the dive.

• Calculate the final partial pressure of oxygen in the tank after the dive.

• Calculate the partial pressure of helium gas in the tank after the dive.

• Model 2 shows the composition of dry air.

• Discuss and illustrate air as a mixture of molecules in the tank in Model 2.

• On a particular day, the air pressure in the chemistry lab is 1.137 atm.

• Calculate the partial pressure of oxygen in the room on that day.

• Calculate the number of moles of oxygen molecules in a 10.0-L sample of air from the room on that day.

• A student wants to burn a 1.00-g sample of ethanol in a jar containing air.

• Calculate the volume of the jar needed to hold enough oxygen for complete combustion.

Page 5:

• Model 3: gas production and collection

  • Gas being produced: O2

  • Gas collection method: trapping gas by putting a tube in the side-arm flask, with the other end submerged in a flask

• Gases present in the bottle after the reaction: H2O and O2

• Mathematical equation for calculating total pressure inside the bottle using partial gas pressures: PTotal = Pwater

• Vapor pressure of water table:

  • Water temperature (°C) - Vapor pressure (mmHg)

  • 20 - 17.5

  • 21 - 18.7

  • 22 - 19.8

  • 23 - 21.1

  • 24 - 22.4

• Determining vapor pressure of water in the gas-collecting bottle in Model 3: 21.1 mmHg = 0.028 atm

• Partial pressure of the gas collected: 0.989 atm - 0.028 atm = 0.961 atm

• Number of moles of gas collected if the volume of the bottle is 1.00 L: 0.961 atm * (1 L) / (0.0821 (L·atm)/(mol·K) * 296 K) = 0.0395 moles

• Discussion on whether Dalton's law holds true if two gases react to form a gaseous product: No, because there would be fewer molecules colliding, resulting in less pressure unless the number of moles of reactants equals the number of moles of product

Page 6:

• Model 4: gas mixture and mole fraction

• Total pressure in the tank: PHe + PAr + PKr = 1.75 atm + 0.35 atm + 0.70 atm = 2.8 atm

• Symbol for mole fraction: Xi

• Mathematical equation for mole fraction: Xi = XA

• Mathematical equation for calculating partial pressure using mole fraction and total pressure: Pi = Xi * PT

• Calculation of partial pressures using the equation: PHC = 0.125 * 2.8 atm = 0.35 atm, Par = 0.250 * 2.8 atm = 0.70 atm, PKr = 0.625 * 2.8 atm =