# GAS STOICHIOMETRY (p. 440 – 443 in text book)

* 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)