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.