Learning Goal 3: Determine the molar proportions of the reactants and products in a balanced chemical reaction.

The Process of using a chemical equation to calculate the relative masses of reactants and products involved in a reaction.› The balanced equation for a chemical

reaction describe the stoichiometry of the reaction.

A unit created to describe atoms because the gram and kilogram are too large to use to define an atom.

1amu = 1.66 x 10-24g .00000000000000000000000166g

Listed on the periodic table as the atomic mass.

The average mass of all of the isotopes of an atom.

Element amu

Hydrogen 1.008

Carbon 12.01

Nitrogen 14.01

Oxygen 16.00

Sodium 22.99

Aluminum 26.98

1 atom = 1 amu Example

› 1 atom of carbon = 12.001 amu of carbon› 3 atoms of carbon = 36.003 amu of carbon› 3.00 X 1020 amu =2.50 x 1019 atoms of

carbon

The unit all chemists use in describing numbers of atoms.

Defined as the number equal to the number of carbon atoms in 12.01 grams of carbon.

A sample of on element with a mass equal to that element’s average atomic mass expressed in grams contains 1 mol of atoms.

6.022 X 1023

One mole of something consists of 6.022 X 1023 units of that substance.

› One mole of eggs is 6.022 X 1023 of eggs.

Elements # of atoms

Mass of sample (g)

Aluminum 6.022 X 1023 26.98

Gold 6.022 X 1023 196.97

Iron 6.022 X 1023 55.85

Sulfur 6.022 X 1023 32.07

Boron 6.022 X 1023 10.81

Xenon 6.022 X 1023 131.3

The MoleThe Mole

The mass of one mole of a substance.› The sum of all the

masses of the atoms in a compound.

CH4

C - 1x12.01=12.01 H – 4x1.008=4.032 Total = 16.04g

The “Y” Diagram is a mnemonic aid for remembering the relationship betweenthe mole and some of the basic quantities used in chemistry. Using a play onwords, students are told to remember to “mole-tiply” out when converting frommoles to other quantities.

Mole

Volume

Particles

Mass Multiply bymolar mass

Divide by molar mass

Multiply by 22.4 l/mole

Divide by22.4 l/mole

Divide by Avogadro's number6.022 X 1023

Multiply by Avogadro's number6.022 X 1023

To move from mass to moles or moles to mass, you must use the molar mass of a compound.

Molar mass gives the mass of one mole of the compound.

Moles Mass› Given moles molar mass (g) = mass of compound

1 mol Mass Moles

› Given Mass (g)1 mol = moles of compound

molar mass (g)

Use the “Y” diagram.› Determine where you are starting.› Follow the arrows to where you are trying to go.

Always show your work and write out each step of the equation.

Use a crossbar.

Make sure to include units.› A number alone has no meaning. You must give it

meaning; use units!

Mole RelationsMole RelationsMole Mole

RelationsRelations