Stoichiometry Lab Part 1– Quantifying Methane Bubbles
Today, you will have the opportunity to light someone on fire… well, at least you will get to light something on fire in
their hands (without lighting them on fire of course!). Before we get started doing this though you will have to prove to
me that you are capable of performing the stoichiometry calculations involved so that I am confident you will only light
the bubbles in the hand on fire without engulfing the person in flames.
When you are confident in your ability to do the necessary stoichiometry calculations ask Mr. Doolan for the
quiz. You must pass the quiz in order to do the lab!
Background:
Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam boiler. Compared
to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. At about 891
kJ/mol, methane's heat of combustion is lower than any other hydrocarbon but the ratio of the heat of combustion (891
kJ/mol) to the molecular mass (16.0 g/mol, of which 12.0 g/mol is carbon) shows that methane, being the simplest
hydrocarbon, produces more heat per mass unit (55.7 kJ/g) than other complex hydrocarbons. In many cities, methane
is piped into homes for domestic heating and cooking purposes.
The overall combustion reaction for methane is: CH4 (g) + O2 (g)  CO2 (g) + H2O (g)
In this experiment one of the few items we have the ability to measure is the volume of the methane. Using the volume
of the methane we can calculate any of the other species in the reaction and calculate how much heat energy is released
from your reaction.
Safety:
You will be working with an open flame today. If you have hair spray in your hair, have long hair and no
scrunchie to pull it back with, or flammable clothing on I suggest that you just observe the reactions today and do not
volunteer to hold the bubbles! Also, if you have long sleeves you may not be the bubble holder either. Since THERE IS AN
INHERENT AMOUNT OF DANGER IN THE LAB TODAY NO HORSEPLAY WILL BE TOLERATED…. NO WARNING WILL BE
GIVEN. IF YOU ACT UP, YOU WILL BE REMOVED FROM THE LAB!
Natural gas has a sulfur agent mixed in with it so that we can smell it. For most people this smell will cause either nausea
and/or headaches. Please be mindful of the amount of gas that you expel into the classroom today. Try to keep it to a
minimum.
Procedure:
1. First we need to set up a soap-water mixture. Add about 200mL of water to the beaker and then add the soap.
You do not want bubbles in your mixture so please mix these gently. Be sure to record the volume of the
water/soap mixture
2. DO NOT TURN THE GAS ON AT THE LAB STATIONS!
3. Put your group name on the queue list and wait for Mr. Doolan to call you to the fume hood.
a. While you are waiting, please complete the sample stoichiometric calculations. These are similar to the
calculations you will be doing at the end of the lab. These will also be turned in with the lab.
4. At the fume hood we will need the following information:
a. Volume of soap water mixture:
b. Volume of bubbles (assume soap has no volume):
5. With the supervision of Mr. Doolan you will be lighting the methane bubbles. Please describe the amount of
heat produced from the combustion reaction in your own words (the more detailed the description the better!)
6. Back at your desks you will quantify the reaction in the following ways (please clean your lab station first):
a. How many moles of methane reacted?
b. What was the mass, in grams, of the methane that reacted?
c. Calculate the mass of oxygen needed to react with the methane
d. Calculate the theoretical yield of water produced from your reaction.
e. Calculate the theoretical yield of carbon dioxide produced from your reaction.
f.
If we needed to produce 200g of water, how much CH4 (in grams) would we need to bubble out? What
would the volume of the bubbles be?
g. How much heat was released from your reaction (in kJ)
h. The volume of methane that we used to today was an approximation since we conveniently ignored the
soap (it does actually have a volume). Come up with a way that we could account for the volume of the
soap and make our calculations more accurate.
i.
How much energy does 1 molecule of methane release when burned?
Interesting question:
The other night I was watching Myth Busters and they blew up a car. Predict how much methane would be needed to
blow up a car. Please quantify your answer and explain what assumptions you are making.
Stoichiometry Calculations to do while you are waiting:
1. __C3H8 + __O2__CO2 + __H2O
a. How many moles of oxygen are necessary to react completely with four moles of propane (C3H8)?
b. Which will produce more water, 25 g of C3H8 or 5 moles of O2?
2. __ C7H6O2 + __ O2  __ CO2 + __ H2O
a. If 16 g of O2 react completely with excess C7H6O2, how many atoms of oxygen are produced?
b. How many moles of oxygen are needed to produce 10 moles of Carbon dioxide?
3. __C2H4 + __O2  __CO2 + __H2O
a. If you start with 45 grams of Ethylene (C2H4), how many grams of Carbon dioxide will be produced?
b. Which will produce more carbon dioxide, 25 grams of oxygen or 25 grams of ethylene?
4. __Mg + __O2 ---> __MgO
a. How many grams of Magnesium oxide are produced when 10.00 grams of Magnesium burn in an excess of
oxygen, as shown above?
b. How many atoms of magnesium are needed to produce 34x1025 molecules of magnesium oxide?