a mole is just a number 6.02 x 10 23 mole. mole map
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A MOLE IS JUST A NUMBER6.02 X 10 2 3
Mole
Mole Map
Molar Density
Density is Mass/VolumeMolar density = Mass of one mole Volume of one mole = Molar Mass 22.4L
Argon= 39.95 g = 1.78g/l 22.4 l
Gas Density
http://www.youtube.com/watch?v=w7G4o2alLww&feature=related
Mole Density and Molar Mass of a Gas Experiment
http://www.youtube.com/watch?v=D0CzquuOrxM
Percent Composition
When the grams are not given, use the molar mass
Molar mass of each element X 100 Molar mass of compound
1.) H—2(1.01)=2.02 S—1(32.06)=32.06 O—4(16.00)=64.00
2). Get total mass2.02 + 32.06 + 64.00= 98.08 (this is bottom #)
3). H 2.02/98.08 X 100= 2.06% S 32.06/98.08 X 100= 32.65% O 64.00/98.08 X 100= 65.25%
Example: H2SO4
Percent Comp by molar mass
http://www.youtube.com/watch?v=JmDd_nJaP3o&feature=related
When mass is given, use mass as part over whole.
Grams element/grams compound X 100
Example: if 64 g of Mg is combined with 32 g oxygen, what is the percent composition?
64 X 100= 66.7 %64 + 32 32 X 100= 33.3%64 + 32
% Comp by mass
http://www.youtube.com/watch?v=DB2YCK2p56o
Empirical Formula Molecular Formula
Consists of the symbols and the subscripts showing the smallest whole number ratio of atoms.
Subscripts are reduced.
May not be the actual formula.
Examples: CO, CO3, N3P
The actual formula.You can reduce the
subscripts.Examples: C2O2,
C2O6, N9P3
Empirical vs. Molecular Formulas
How do you calculate empirical formulas?
1. Change the % sign into a g. (g for grams)2. Divide mass by molecular weight(convert
grams into moles)3. Divide by the smallest.4. If necessary, multiply to make whole
numbers.5. These are your SUBSCRIPTS.
Example of empirical formulas.
Find the empirical formula of a compound found to contain 63.52% Fe and 36.48% S.
63.52 g Fe = 36.48 g S = 55.85 g 32.07
g
Fe1S1
Example #2
Find the empirical formula of a compound found to contain 26.56% K, 35.41% Cr, and the remainder O.
26.56 g K
35.41 g Cr
38.03 g O
Empirical to Molecular
X(empirical formula) = molecular formulaX = molecular weight of molecular formula molecular weight of empirical formulaExample: The empirical formula of a compound
of P and O was found to be P2O5. The molar mass of the compound is 283.89 g/mol. What is the molecular formula?
1. Find the molecular weight of the empirical formula.
2. Divide molecular/empirical.3. Multiply x by empirical formula.
Example
http://www.youtube.com/watch?v=LPN-3d0FOMU
Determine the molecular formula for a compound that is 40.0% C, 6.6% H, and 53.4 % O. The molar mass is 120 g.
Determine the molecular formula of a compound with an empirical formula of CH and a formula mass of 78.110 amu.
Practice
1. Find the percent composition of Mg(OH)2.2. Find the percent composition of a
compound that contains 1.94g C, 0.48g H, and 2.58g S in a 5.0g sample.
3.Determine the empirical formula of a compound containing 1.723gC, 0.289gH, and 0.459gO.
4. Find the molecular formula of a compound that contains 30.45gN and 69.55gO. The molar mass is 92.02g/mol.
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