CHEMISTRY LAB: COMPOSITION OF NATURAL GAS
(NATURALGAS.docx)
Name: _____________________
Date: ______________________
1. Introduction: America is blessed with a wealth of natural resources, one of which is large
amounts of natural gas. In 2011, America got 25% of its energy from natural gas. Most of it is
used as a fuel, either directly to provide heat or indirectly to be used in gas-turbine-powered
electrical generators (31%). It is used in our chemistry laboratory in the familiar Bunsen burner.
a. Most of America’s natural gas is found in 33 states. It is distributed from the wells to
processing plants and on to users throughout the nation using a system of underground pipelines.
(Perhaps you have seen the safety markers; they are white pipes with an orange tip.)
b. In 2011, the U.S. production of natural gas was 24.37 trillion cubic feet (Tcf). The top
six producing states account for a little over two-thirds of our production: Texas, Wyoming,
Oklahoma, New Mexico, Louisiana, and Colorado.
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c. Your task in this activity is to identify the gas by name, using its molecular weight as
the key. Your knowledge of the gas laws will be essential to reaching a conclusion.
2. Safety: Avoid inhaling the burner gas. Do not allow any open flames or spark-making
devices in the lab during this activity. Rinse your hands before leaving the lab for any reason.
3. Materials and Supplies Needed:
a. From the prep area:
thermometer
length of latex tubing
two-liter soda bottle with cap
b. From your supply cupboard:
pneumatic trough
100-ml graduated cylinder
c. At your lab bench:
electronic scale
d. Laboratory apron and safety goggles for each member of your lab team.
4. Procedure:
a. Don your safety equipment and leave it on until the lab is over and clean-up is
complete.
b. Use the latex tubing to connect the gas valve to the inlet fitting on the bottom of the
trough. Set the trough in the sink and fill it with tap water.
c. Mass the empty (air only) bottle with its cap and record in the data section in
paragraph 5, below. Determine the local barometric pressure reading using the internet and
record. Record the air temperature in the lab.
d. Fill the bottle to overflowing with tapwater. Tap on the bottle to dislodge any bubbles
and refill with water. Measure the volume of the bottle by pouring the water in portions into the
graduated cylinder and adding up all the volumes to get a total for the bottle. Record.
e. Refill the bottle completely and secure with the cap. Invert it in the trough and
remove the cap while under water. Keep the neck of the bottle under water so no air enters.
Open the gas valve and let some gas flush the air from the latex tubing. When you believe only
pure gas is coming through, hold the bottle over the gas inlet and collect natural gas in the bottle
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until it is completely full. Turn off the gas. Secure the cap and remove the bottle from the water.
Dry the outside of the bottle. Mass the capped bottle and record.
f. Empty the bottle outside or into an operating fume hood. Return borrowed equipment.
Clean up your work area. Fold and return the lab apron. Return the goggles to the sterilizer
cabinet. Rinse your hands,
5. Data:
a. Mass of bottle and cap (filled with air):
__________ grams
b. Barometric reading:
__________ inches Hg
c. Air temperature in laboratory:
__________ degrees Celsius
d. Volume of bottle:
__________ milliliters
e. Mass of bottle and cap (filled with natural gas):
__________ grams
f. Density of air at 1 atmosphere and 15 deg Celsius:
1.225 grams / liter
6. Calculations:
a. Convert the local air pressure from inches Hg to atmospheres:
(Use 1 atm = 29.92 in Hg.)
__________ atm
b. Convert the bottle volume from milliliters to liters:
__________ L.
c. Convert the temperature from Celsius to Kelvin:
__________ K
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d. Use the gas laws to calculate density of air at laboratory conditions:
(Hint: See 5f. Calculate the new volume once the air has achieved lab
conditions. What is its density now that its mass has achieved the new volume?)
__________ g / L.
e. Calculate the mass of the air in the bottle:
__________ g
f. Calculate the mass of the bottle and cap (without any air):
__________ g
g. Calculate the mass of the natural gas in the bottle:
__________ g
h. Use the ideal gas law to calculate the moles of natural gas in the bottle:
(n = PV / RT, where R is 0.08205 when measuring pressure in atm)
__________ mol
i. Calculate the molecular mass of natural gas:
__________ g / mol
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7. Analysis: The three gases that are most likely to occur in natural gas are listed below.
Calculate their molar masses.
Gas:
Formula:
Molar Mass (g/mol):
Methane
CH4
__________
Ethane
C2H6
__________
Propane
C3H8
__________
8. Conclusion: Determine which gas is most likely the major component of natural gas.
Gas: _______________________________
9. Extension:
a. Convert 24.37 trillion cubic feet into cubic meters. (Use 1 inch = 2.54 cm, the legal
definition of the inch.)
__________ m3
b. When burned, methane produces a theoretical yield of 891 kilojoules per mole. If
America burned all the methane it produced in the year cited, how many joules of heat energy
would have been released? (Assume natural gas is pure methane, and use 22.4 L per mole.)
__________ J
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LAB NOTES:
(Note: National data is from 2011.)
7. Molar masses:
Methane
16.04 g/mol
Ethane
30.07
Propane
44.10
8. Natural gas is only about 87% methane, so there will have to be some approximating here.
9a. 6.90 x 1011 m3
9b. 2.74 x 1019 J
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