OUTLINE:
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!!!
molecules<------------->MOLES<-------------------->grams
Av.# / 1 mole molar mass (from P.T.)
1mole / Av # g/mole (or 1 mole/?g)
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*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!
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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.
ARE YOU READY FOR A TEST!?!?!?!?
Try links below for more notes and practice. The practices have answer pages too.
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