molesetc Me
Main Page
Chapter 4: pages 121-135 Review Q's in the book are a good self test.

Go To Outline w/ hyperlink notes (good one w/ extra practice & notes!)

Avogadro's number: 6.023 E23

Mole: Avogadro's number of anything.
     A mole of marbles = 6.023 E23 marbles
     A mole of gummy bears = 6.023 E23 gummy bears

Molar Mass: (g/mol) Mass of one mole.  Equal to atomic weight but measured in grams. (Get from P.T.)

Molecular Weight: Sum of all atomic weights in a molecule.

Formula Weight: Same as Molecular Weight (but does not imply molecular (non-metal/non-metal) bonds.

    The Reason for The Mole Go To:2 Worlds of Chemistry
    You can practice w/ Mole Calculations good examples w/answers and practice!!!

              Av.# / 1 mole         molar mass (from P.T.)
              1mole / Av #          g/mole (or 1 mole/?g)

*write down what I give you
*look at what I am asking (look at units!)
*Use the proper conversion(s)
*Take it step by step!

Molarity: Concentration in moles per liter.

     If I ask for concentration or molarity, get moles on top and liters on the bottom.  (start w/ what can get moles over one.  Once you have moles, divide by the volume.

     ALL OF THE REST OF THE TIME when doing molarity problems, USE the molarity as a conversion factor (moles<-->liters).

Percent Composition: (Part) DIVIDED BY (Whole) X 100%

     Get atomic masses from the P.T. (parts).  Add them up (don't forget to multiply by the subscripts) to get the whole.

Empirical Formula: The LOWEST whole number RATIO of elements in a compound.

***Convert to moles!!!***Use the P.T.
If you were given percents, assume 100g.  That way the masses are the same as the percents!

Molecular Formula: The actual ration in which elements hook up in a compound.

To determine Molecular formula, you need 3 things!
Empirical formulas
EFM-empirical formula mass
MM-molar mass (given in question)

Step #1 - MM/EFM = # (a magical whole number)
step #2 - multiply the subscripts of the empirical formula by the magic number

If you are not given the empirical formula, figure it out!
1>Get Moles of each element!!!!!
If I give you grams, great, use the PT to get the atomic mass of each.  24 g C 1 mole = 2 moles C
                       12g C
2>Write the wierd Eq (element symbols w/ moles as subscript)

3> Divide ALL subscripts by the smallest.
Multiply by 2,3,4 or 5 IF NEEDED.

Don't round until the very end!  Only round if it is .9something or .osomething.

Try links below for more notes and practice.  The practices have answer pages too.
My Quia activities and quizzes
Moles "The Beginning"
in progress
Moles!!!!!: session moles
Will you just type in moles-PLEASE!
Too Many Moles!!!!
for the test test test test...
Useful links
Last updated  2008/09/28 05:23:08 PDTHits  4404