Lab on Avogadros Law

1. Take a gas piston from the Glassware shelf and place it on the workbench. The gas piston is like a syringe, except that the piston/plunger is free to move up and down in order to equalize the pressure of its contents with the outside room pressure.

2. Take a balance from the Tools shelf and drop it on the gas piston. Record the mass of the empty gas piston.

3. Select a gas from the Chemicals shelf and fill the gas piston with 100 mL of the gas. Weigh the gas piston and gas and record the total mass.

4. Take four more gas pistons from the Glassware shelf and fill them each with 100 mL of one of the other four gases on the Chemicals shelf.

5. Weigh and record the total masses of each piston with gas.

6. Open the Data window and click on each gas piston. Record the molecular weight (MW) of each gas.

Questions

1. Record the mass of the empty gas piston (g):

2. For each gas, record the following:

(a) Name and formula
(b) Mass of gas piston and 100 mL gas (g)
(c) Mass of 100 mL gas (g)
(d) Molecular weight of the gas (g/mole)
(e) Number of moles in the 100 mL sample

% deviation = |(moles of gas) - (average for all gases)| / (average for all gases) * 100%

(a) Average number of moles in 100 mL for all five gases:
(b) % deviation for each gas:
(c) Do your results confirm Avogadro's Law?

4. Volume occupied by one mole of gas at STP. One mole of any gas at STP conditions (standard temperature and pressure) occupies 22.4 liters. See how well the average number of moles for the gases agrees with this.

(a) Calculate the volume occupied by one mole of gas from the average number of moles in the 100 mL volume using the following proportionality equation:

average moles / 100 mL = 1 mole / (volume of 1 mole)

(b) You should get something close to 22.4 L. This number must then be corrected for non-STP conditions in the lab as follows. Click on the wall chart at the top of the lab (just under the lab title) to view the current temperature and pressure in the room. For ideal gases, PV/T is constant, and at STP, P=1 atm, V=22.4L, T=273.15K (0C). Solve for the corrected volume at the lab temperature and pressure. Recalculate the expected moles in the corrected volume at lab temperature and pressure. Report your experimental results using the corrected volume for 1 mole of gas, along with the percent deviation.

(c) Explain what might have caused your value to differ from the accepted value.