“Moles”

MOLE is a way of translating

between grams and amu’s

•a mole is a number that helps us translate between the atomic world and our every day world

•specifically “6.02 x 1023”

•known as:

“Avogadro’s Number”

MOLE is a direct translation

between grams and amu’s

•1 mole of an atom’s amu = 1 g

•1 gram = 6.02 x 1023 amu = 1 mole

•(e.g.) carbon-12 [12C] = 12 amu

12 amu = 6.02 x 1023 of carbon atoms

6.02 x 1023 of 12C = 12 grams

1 gram of 12C = 1 mole of 12C

MOLES and GRAMS

•1 mole of an atom’s amu = 1 g

•1 gram = 6.02 x 1023 amu = 1 mole

Fe = 55.86 = 56 amu

56 amu = [56Fe] 56 amu x 6.02 x 1023 = 1mole

1 mole of 56Fe = 56 g

26

Feiron

55.85

MOLES and GRAMS

•1 mole of an atom’s amu = 1 g

•1 gram = 6.02 x 1023 amu = 1 mole

Si = 28.09 = 28 amu

28 amu = [28Si] 28 amu x 6.02 x 1023 = 1mole

1 mole of 28Si = ___ g

14

Sisilicon

28.09 28

MOLES and GRAMS

•1 mole of an atom’s amu = 1 g

•1 gram = 6.02 x 1023 amu = 1 mole

Si = 28.09 = 28 amu

28 amu = [28Si]

28 amu x 6.02 x 1023 = 1mole

2 moles of 28Si = ___ g

14

Sisilicon

28.09 56

MOLES and GRAMS

•1 mole of an atom’s amu = 1 g

•1 gram = 6.02 x 1023 amu = 1 mole

O = 15.999 = ___ amu

16 amu = [16O] 16 amu x 6.02 x 1023 = _ mole

4 moles of 16O = ___ g

8

Ooxygen

15.999 64

16

1

MOLAR MASS

•EQUALS the MASS of “1” MOLE of a substance

•it is the MASS of “1” MOLE of a single TYPE OF ATOM (an element)

•if the substance consists of a molecule, the molar mass is the MASS of each individual atom in that molecule / compound

•Molar Mass is measured in grams per mole (g/mol)

MOLECULAR MASS

•is the combined MASS of the group of atoms forming a SINGLE MOLECULE (smallest unit of a compound)

•FIND by “adding” the MASSES of the atoms forming the molecule

•Molecular Mass is measured in grams per mole (g/mol)

GRAMS per MOLE

•g/mol how the number of GRAMS of “1” MOLE of any substance would feel

•(e.g.)

Molecular Mass of CO2 = 44 g/mol

•EXPLANATION:

If you had “1” mole of a CO2 molecule,

its mass would be 44 g (the feel of “44” USA dollar bills stacked in your hand)

MASS in AMU

•you can express the MASS of an ATOM (ELEMENT) or a single molecule

(COMPOUND) in AMU (atomic mass units)

•(e.g.) 12C = 12 amu = 1 mole 12C = 1 mole = 6.02 x 1023 12C = 12 amu = 12 g/mol = 12 g

FINDING MOLECULAR MASS:

•1st look up the Average Atomic Masses of the molecule’s component ELEMENTS on the Periodic Table

•2nd round each Average Atomic Mass to the nearest WHOLE number

•3rd use the ATOMIC MASS of each ATOM per ELEMENT in the COMPOUND

•4th find the TOTAL SUM

EXAMPLE – Finding Molecular Mass

in AMU:

CO2

C = 12.01 = 12 amu

O = 15.999 = 16 amu

CO2 = 1 (C atom) + 2 (O atoms)

CO2 = 1 (12 amu) + 2 (16 amu)

CO2 = 12 amu + 32 amu

CO2 = 44 amu

8

O oxygen

15.999

6

Ccarbon

12.01

CONVERTING amu to g/mol:

•seldom refer to MOLECULAR MASS in amu units, but rather in g/mol

•to convert amu to g/mol just simply change the units FROM amu TO g/mol

•“1” MOLE of any type of ATOM has a MASS in grams EQUAL TO the ATOM’s MASS measured in amu

EXAMPLE – Converting amu into

g/mol:

CO2

C = 12.01 = 12 g/mol

O = 15.999 = 16 g/mol

CO2 = 1 (C atom) + 2 (O atoms)

CO2 = 1 (12 g/mol) + 2 (16 g/mol)

CO2 = 12 g/mol + 32 g/mol

CO2 = 44 g/mol

8

O oxygen

15.999

6

Ccarbon

12.01

Avogadro’s Number: 6.02 x 1023

Amedeo Avogadro •Italian physicist (1811)

•discovered that equal volumes of different gases contain equal numbers of molecules if pressure and temperature are kept constant

•Avogadro’s number = 6.02 x 1023 particles/mole

•Avogadro's number can be applied to any substance since it corresponds to the number of atoms/molecules needed to make up a mass equal to the substance's atomic or molecular mass in amu which then converts into g/mol

AVOGADRO’S NUMBER

and MOLES:

HAPPYMOLEDAY Oct 23rd