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Unit 13, Worksheet 3
Stoichiometry with Combustion
Name __________________________
Date __________ Hour ________
Earlier in the year, we learned a couple of patterns (single replacement, double replacement) for
predicting the products in a chemical reaction. On this assignment, you will be using another pattern –
combustion (burning) of simple organic compounds.
Organic compounds are those compounds that contain carbon and hydrogen. In addition,
organic compounds often contain other nonmetal elements like oxygen, nitrogen, sulfur, phosphorus,
and halogens. For the time being, we will focus on those compounds that contain just carbon and
hydrogen (called hydrocarbons) and those that contain carbon, hydrogen, and oxygen.
When a compound that contains just carbon and hydrogen (or one that contains carbon, hydrogen,
and oxygen) is burned, it reacts with oxygen to produce carbon dioxide gas and water vapor. Use
the following tips for balancing combustion reactions:
a. Balance oxygen last. You can put a coefficient in front of the O2 without messing up
the C and H that you’ve already balanced.
b. It might be necessary to put a 2 in front of the compound that is being burned. It will
never be necessary to put any other coefficient in front.
c. For compounds that contain carbon, hydrogen, and oxygen, don’t forget to count the
oxygen(s) in the compound that is burning.
Answer the following questions completely. Be sure to show all unit conversions as you’ve been
taught, include units, and round answers to the proper number of significant figures. All reactions are
occurring at STP.
1. Given the equation below showing the combustion of pentane, answer the following questions:
C5H12 (g) +
O2 (g) 
CO2 (g) + H2O (g)
a. Balance the above equation using lowest whole number coefficients.
b. What mass of water is formed when 0.845 moles of pentane are reacted?
c. What volume of carbon dioxide is formed when 3.58 grams of oxygen gas react?
d. What mass of pentane is needed to produce 13.8 L of carbon dioxide gas?
2. Butene is a hydrocarbon with molecular formula of C4H8.
a. Write a balanced equation for the combustion of butene.
b. What mass of carbon dioxide is formed in a reaction that forms 12.92 grams of water?
c. What volume of oxygen gas is needed to react with 12.7 g of butene?
d. What volume of carbon dioxide would be expected to be produced when 92.3 L of
oxygen reacts?
3. Complete and balance the equation below which represents the combustion of ethanol.
a.
C2H5OH (l) +
O2 (g) 
CO2 (g) +
H2O (g)
b. How many moles of oxygen are needed to react with 192 g of ethanol?
c. What volume of carbon dioxide gas can form when 1.93 moles of oxygen react?
d. What volume of water vapor would be expected to be produced when 12.7 g of oxygen
reacts?
4. Complete and balance the equation below which represents the combustion of hexane.
a.
C6H14 (l) +
O2 (g) 
CO2 (g) +
H2O (g)
b. How many grams of oxygen gas are needed to completely react 91.3 grams of hexane?
c. What volume of carbon dioxide gas can form when 2.75 grams of oxygen react?
d. What mass of water would form at the same time that 52.1 L of carbon dioxide form?
5. Complete and balance the equation for the combustion of methyl ethyl ether.
a.
CH3OC2H5 (l) +
O2 (g) 
CO2 (g) +
H2O (g)
b. What mass of water can form when 6.72 grams of methyl ethyl ether reacts?
c. What mass of water can form when 38.2 L of oxygen reacts?