For this assignment you will need access to BeyondLabz. I will give you the information needed to get access to the program.In this simulation you will fill a balloon with a mixture of gases, controlling the amount of each gas that you add. You will examine the pressures of the gases in the mixture and demonstrate the relationship between partial pressures and total pressure of a mixture (Dalton’s Law of Partial Pressures).
5-5: Dalton’s Law of Partial Pressures
Dalton’s Law of Partial Pressures, named after its discoverer John Dalton, describes the behavior of gas mixtures. It states that the total pressure of the gas, Ptot, is the sum of the partial pressures of each gas, or the sum of the pressures that each gas would exert if it were alone in the container. In this assignment you will become more familiar with Dalton’s law.
- Start Virtual ChemLab, select Gas Properties, and then select Dalton’s Law of Partial Pressures from the list of assignments. The lab will open in the Gases laboratory. You will see a gas experiment with eight gas cylinders on the right. Make certain that the switch on the lower right of the lab bench is set to Ideal Gases. Note that the Ideal Gases each have a different molecular weight.
- Select one of the Ideal Gas cylinders by clicking on the white label. Click the red arrow on the brass cylinder valve until the meter reads 400. Add this Ideal Gas to the balloon by clicking the green Open Valve switch once to add gas and again to stop. Add an amount of your choice but do not fill the balloon too full since you will be adding two additional gases. Click Return Tank.
- Repeat step # 2 for two additional Ideal Gases of your choice. Make certain that you do not explode the balloon. If you do, click the Reset button located on the upper right of the gas chamber and repeat the experiment.
- Click on the experimental apparatus to Zoom In. There are four LCD controllers on the left for volume, pressure, temperature, and number of moles. You can change the units for volume, pressure, and temperature by clicking on the Units button on each controller. Under pressure and number of moles are numbers 1-8 that correspond to Ideal Gases 1-8. The three gases that you selected will be highlighted. Clicking on each highlighted number will display the pressure or moles for that gas alone. Find the Ideal Gas number, the number of moles, and the partial pressure for each of your three Ideal Gases. Record this in the data table below.
Ideal Gas Number
Partial Pressure (Pi)
- Using the information from the data table, determine the total pressure in the balloon. Show your work here.
- Click Total on the Pressure controller of the experimental apparatus. Record the value displayed here:
- Compare your answer from # 5 to the total pressure on the meter record from step 6. Write a mathematical equation to represent what you have learned about Dalton’s Law.
- Another way of expressing Dalton’s Law of Partial Pressures is with the expression:
Pi = xiPtotal
where Pi is the partial pressure of gas i xi is the mole fraction of gas i in the gas mixture and Ptotal is the total pressure.
Recall that mole fraction of gas i, xi = moles of gas i / total moles of gas in mixture
Verify that this relationship holds using the data you have collected and record you results in the data table below.
Ideal Gas Number
Show your work here.