1. Chapter 9 By the end of this section you will… –Be able to define stoichiometry –Be able to generate a mole ratio and use it to relate different substances in a given reaction –Determine which reactant determines the amount of product that will be made –Be able to identify daily experiences that apply the theory of stoichiometry

2. Think on this… How would you prepare the ultimate s’more? Write an equation that represents the perfect combination of graham cracker, chocolate and marshmallow! __G + __C + __M  1 GCM (GCM = s’more)

3. Ratios Just like there is a preferred amounts of graham, chocolate and marshmallow in preparation of a s’more there are ideal amounts of each substance needed for a chemical reaction to be carried out. We show these amounts via coefficients in a balanced equation.

4. Where does the ratio come from? The ratio comes from the coefficients in the balanced equation… 2 Mg + 1 O 2  2 MgO Write the ratios for each pair of substances: Mg:OMg:MgOO:MgO : : :

5. Stoichiometry? The study of quantitative relationships that exist between various substances in a chemical reaction (or equation) The bridge between any pair of substances is the mole ratio!

6. Where does this impact life? Stoichiometry (ratios) are everywhere around us. –Recipes –Cars –Your body –Your Home

7. Keys to Conversion There are several relationships that must be understood to succeed in relating different substances involved in a reaction. –Mole Ratios –Molar Mass –Avogadro’s # (6.02 x 10 23 units) –Molar Volume (we will discuss this later)

8. The Math of Stoichiometry Think back to the first chapter of the year, can you remember converting between units in the metric system? Stoichiometry is a conversion…we use known information about one substance to determine various information about a second substance in the reaction.

9. D.A. Dimensional Analysis is a way of using ratios to generate conversion factors that allow us to take the mass/# moles of one substance in an equation and determine the mass/# moles of a second substance. A conversion factor is a fraction that allows us to change from one label to another when we multiply by it.

10. Example If we know that 2.00 moles of oxygen were reacted with excess magnesium to produce magnesium oxide…how may moles of MgO were made? 2 Mg + 1 O 2  2 MgO Mole ratio  2 mol MgO : 1 mol O 2 2.00 mol O 2