Physical Science Institute
Summer 2013
Counting On Gases-Teacher Guide
MATERIALS
(1) balance, top-loading with a minimum precision 0.001g
(1) oxygen canister w/ valve, 1/8” ID tubing connected to female luerloc-to-200 series barb fitting
(1) MAPP canister w/ valve, 1/8” ID tubing connected to female luerloc-to-200 series barb fitting
(1) butane canister with 1/16” ID tubing connected to female luerloc-to-classic barb fitting
(1) duster canister with 1/16” ID tubing connected to female luerloc-to-classic barb fitting
(1) 140cc syringe w/ nail stop
(1) syringe tip cap
Century Cleaning Duster, 10 Oz / Office Depot / 448938BernzOmatic butane refill / Lowes / 332077
Balance, top-loading / Fisher / S94792K
Syringe, Luer loc 140cc with nail lock / S17 Science / EQ 089
Syringe tip cap / Flinn / AP8958
Luer lug (female) to 200 series barb / Value Plastics / FTL240-9
Female Luer Lug Style to Classic Series Barb, 1/16" (1.6 mm) ID Tubing, Clear Polycarbonate / Value Plastics / FTL10-9
Tygon® Tubing R-3603 1/16" ID x 1/8" OD x 1/32" Wall / US Plastics / 57102
Tygon® Tubing R-3603 1/8" ID x 3/16" OD x 1/32" Wall / US Plastics / 57104
BernzOmatic Torch Kit / Grainger / 4LFJ4
Balance, top-loading / Fisher / S94792K
NOTES
· To make the valve assemblies, cut the tubing off the valves found in the Bernzomatic Torch kit. This will give a valve for both the MAPP and oxygen gas setups.
· Make sure syringe plungers aren’t sticking. If they are, lubricate the plunger with silicone grease.
· The valve assembly for the oxygen canister has left-handed threads. Lefty-tighty, righty-loosey.
Pictures of the gas canister setups with tubing and Luer-loc connector:
Butane setup:
Duster setup
MAPP setup:
Oxygen setup:
CALCULATIONS AND RESULTS
1) Participant results will vary.
2) Participant results will vary.
Accepted molecular mass of gases used:
Butane (C4H10) = 58
MAPP (C3H4) = 40
MAPP is a mixture of methyl acetylene, propadiene, and propane. The average molecular mass for this mixture is very close to propyne.
Duster gas:
Freon 134a (1,1,1,2-tetrafluoroethane) = 102
or
Freon 152a (1,1-difluoroethane) = 60
Check the label of the duster canister to determine the gas being used.
3.
Name of gas / Molecular mass from Table 4.3 column (4) / Mass of gas needed to have the same number of molecules as are in 32.0 g of oxygen gas / Mass of gas needed to have the same number of molecules as are in 16.0 g of oxygen gas / Mass of gas needed to have the same number of molecules as are in 22.0 g of carbon dioxide gas / Mass of gas needed to have the same number of molecules as are in 32.0.0 g of methane gashydrogen bromide / 80.9 / 80.9 grams / 40.5 grams / 40.5 grams / 162 grams
carbon dioxide / 44.0 / 44.0 grams / 22.0 grams / 22.0 grams / 88.0 grams
oxygen / 32.0 / 32.0 grams / 16.0 grams / 16.0 grams / 64.0 grams
nitrogen / 28.1 / 28.1 grams / 14.0 grams / 14.0 grams / 56.2 grams
ammonia / 17.0 / 17.0 grams / 8.50 grams / 8.50 grams / 34.0 grams
methane / 16.0 / 16.0 grams / 8.00 grams / 8.00 grams / 32.0 grams
hydrogen / 2.02 / 2.02 grams / 1.01 grams / 1.01 grams / 4.04 grams
EXTENSION:
Because oxygen gas is diatomic (O2), the total number of nucleons in this molecule for the most abundant isotope of oxygen is 32 (8 protons & 8 neutrons for each oxygen atom). The proton and neutron have masses close to 1.0 on the relative weight scale. The relative masses of most elements are close to the number of nucleons when one of the isotopes is considerably more abundant.