Gas Stoichiometry at STP
Objective: calculate chemical quantities using BOTH a balanced chemical equation and the molar volume of a gas
in one factor label problem
Background Information
The Volume of a Gas
Conclusion: Gases can be compressed and expanded. The volume of a gas must also include
pressure. Kinetic Theory states that pressure and temperature are directly related,
therefore the volume of a gas must include temperature.
define STP- standard temperature and pressure
standard temperature- 0˚C
which is the same as 273 K
°C + 273=K
standard pressure- 1 atm, 10.3 kPa, 760 mmHg
T. O’Toole
Example #1
When .85 grams of magnesium react with hydrochloric acid, how many L of gas are
produced at STP?
.85 g Mg x
1 mole Mg
24.3 g Mg
x
1 mole H
22.4 L H
2 x
2  .78 L H
2
1 mole Mg 1 mole H
2
Example #2
When 1.0 L of oxygen is produced at STP, how many molecules of potassium chlorate are
decomposed?
1.0 L O 2 x
1 mole O 2 2 mole KClO3 6.02x10 23 molecules KClO3
x
x
 1.8x10 22 molecules KClO3
22.4 L O 2
3 mole O 2
1 mole KClO3
YOUR TURN:
If 15.0 ml of .25M acetic acid was used to react with sodium bicarbonate, how many L of
gas would be produced at STP?
HC2H3O2 + NaHCO3  NaC2H3O2 + CO2 + H2O
.25 mole 1 mole B 22.4 L
15.0 ml x
x
x
 .084 L
1000 ml 1 mole A 1 mole
Minute Paper: If 100.0 grams of lithium are added to water, what volume of gas could be
collected at STP?
How do I get from where I am to where I’m going?
10 Minute Makeover Customize your learning by choosing from the following options each night:
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Complete the “Calculate with Gases” section on the Portfolio Page
Review the PPT file on the website
QUIA flashcard practice (http://www.quia.com/jg/1337564.html)
Read pages 247-250 and 347-349 in the book
Extra practice problems: page 262 #41c and 53-answers in Appendix C
Extra practice problems: page 356 #63-answer in Appendix C
Check out the tutorial sources in the LiveBinder
Complete the SYS Assignment
Review the skills from today’s Train Your Brain
T. O’Toole