* chemical
reaction is happening
* deals with two different substances (at least 1 is a gas)
* given chemical equation
* assume reaction occurs at STP unless otherwise noted
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STOICHIOMETRY STEPS
~ Balance the
equation
~ Write the important information from the problem
1st addition to
“train tracks”: use
molar mass of given substance (if given a # of grams) or
use 22.4 L =
1 mole of gas @ STP (if given liters)
2nd addition to
“train tracks”: use
coefficients in the mole ratio
3rd addition to
“train tracks”: use
molar mass of unknown substance (if problem asks for grams) or
use 22.4 L =
1 mole of gas @ STP (if problem asks for liters)
Example # 1
How many
Liters of carbon dioxide gas can be produced from the decomposition of 4.50
grams of sodium carbonate?
Na2CO3 à Na2O + CO2
4.50 g Na2CO3 | 1
mole Na2CO3 |
1 mole CO2 | 22.4 L CO2 = 0.951 L CO2
| 106 g Na2CO3 | 1 mole Na2CO3
| 1 mole CO2
Example # 2
How many grams
of aluminum are needed to completely react with 16.0 L of oxygen?
Al + O2
à Al2O3
(Ans: 25.7 g)
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