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 g  g

 Listed on the periodic table as the atomic mass.  The average mass of all of the isotopes of an atom. Elementamu Hydrogen1.008 Carbon12.01 Nitrogen14.01 Oxygen16.00 Sodium22.99 Aluminum26.98

 1 atom = 1 amu  Example › 1 atom of carbon = amu of carbon › 3 atoms of carbon = amu of carbon › 3.00 X amu =2.50 x 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 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.

 X  One mole of something consists of X units of that substance. › One mole of eggs is X of eggs. Elements# of atoms Mass of sample (g) Aluminum6.022 X Gold6.022 X Iron6.022 X Sulfur6.022 X Boron6.022 X Xenon6.022 X

The Mole

 The mass of one mole of a substance. › The sum of all the masses of the atoms in a compound. CH 4  C - 1x12.01=12.01  H – 4x1.008=4.032  Total = 16.04g

 The “Y” Diagram is a mnemonic aid for remembering the relationship between the mole and some of the basic quantities used in chemistry. Using a play on words, students are told to remember to “mole-tiply” out when converting from moles to other quantities. Mole Volume Particles Mass Multiply by molar mass Divide by molar mass Multiply by 22.4 l/mole Divide by 22.4 l/mole Divide by Avogadro's number X Multiply by Avogadro's number X 10 23

 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 molesmolar 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 Relations Mole Relations