 # CHEMISTRY Look Here! Unit Factoring Help

"Unit Factoring" is also called "Dimensional Analysis" or the "Factor Label" method.  It is useful when converting from one set of units to another, when changing units in a rate, or when doing stoichiometry.  Here are some online resources that might help you if you are still stuck on some aspect.

Remember, working a "Level 4" Problem means YOU can determine conversion factors AND choose and place the correct conversions to answer your question.

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HINTS:

If your START substance and END substance are DIFFERENT SUBSTANCES, you will need a mole-mole ratio.

If you have grams (MASS) anywhere in the problem, you will need a PERIODIC TABLE and a molar mass.

If you have Liters (VOLUME) of a gas, you will need the 1 mol __ = 22.4 L __ conversion factor (thanks, Avagodro).

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TO SOLVE:

Moles of A to Grams of A:   one step, molar mass from periodic table

Grams of A to Moles of A:  one step, molar mass from periodic table

Moles of A to Moles of B:  one step, mole-mole ratio**

Grams of A to moles of B:  more than one step, using molar mass from periodic table and mole-mole ratio**

Moles of A to Grams of B:  more than one step, using mole-mole ratio and molar mass from periodic table**

Grams of A to Grams of B:  at least three steps, using molar mass from periodic table, mole-mole ratio, and another molar mass from periodic table  **

**There are times when more than one mole-mole ratio is needed in the middle of a problem.

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VIDEOS AND RESOURCES WHICH MIGHT BE HELPFUL TO SOME STUDENTS:

Unit Factoring Basic Problem (one version) (11:13)

Stoichiometry lesson by Bozeman Science (9:45)

Stoichiometry by Crash Course in Chemistry (12:46)  "Stoichiometry: Chemistry for Massive Creatures - Crash Course Chemistry #6"

Lecture covering the process of "Moles A to Moles B and Grams A to Grams B Stoich"  (11:38)  Several examples are written out and narrated step by step.

How to Understand Conversion factors by Tyler Dewitt (10:13) Emphasizes the rationale behind the mechanics of what we are doing

Still want more?  Try these search terms:

• stoichiometry
• unit factoring
• factor label method
• dimensional analysis
• how to convert grams to moles
• how to convert grams of A to grams of B
• molar mass
• mass ratio
• balanced equations
• conversion factor

(You may also find additional video links when watching any of the above videos.)

How to Determine MOLE RATIOS

Lecture style with board notes (5:37)

How to Calculate MOLAR MASS

Step by step (8:49)

Slow paced (3:00)

For help with metrics using the same format, try this site: http://www.youtube.com/watch?v=w0nqd_HXHPQ&feature=related

For basic help with metrics, try this http://www.youtube.com/watch?v=SYkmadc2wOI&feature=fvwrel   (But you still have to memorize the prefixes!!!)

Here is another series covering similar material: http://www.youtube.com/watch?v=Vyr20KfKKU4&feature=related

For an advanced example of unit factoring in the real world... http://www.youtube.com/watch?v=ScvuRb6vsz4&feature=relmfu

And finally, for stoichiometry (there's that word again!), look at this example...http://www.youtube.com/watch?v=eQf_EAYGo-k&feature=relmfu Happy Factoring!