1. LIKE BAKING A CAKE

2. 2 If reactants are added to a container in amounts that differ from the required reaction stoichiometry then some reactants will not be completely used in the reaction. Limiting Reactant (Reagent) The reactant that is entirely consumed in a reaction. The reaction stops when the limiting reactant is used up. Excess Reactant (Reagent) The reactant(s) that are left over after a reaction is completed. 1. What is a Limiting Reagent?

3. Baking a cake: 2 cups flour + 1 egg → 1 cake 4 cups flour + 2 eggs? How many cakes? = 2 cakes 2 cups flour + 2 eggs? How many cakes? 2 cups flour + 2 eggs → 1 cake 1 egg The amount of product formed is determined by the starting amount of the limiting reagent. 3 Examples of Limiting Reactants

4. Pb(NO 3 ) 2 (aq) + 2KI(aq) → PbI 2 (s) + 2KNO 3 (aq) 4 2. Examples of Limiting Reactants KI is limiting Pb(NO 3 ) 2 is limiting

5. N 2 + 3 H 2  2 NH 3 2 molecules of NH 3 will be produced when 3 molecules of H 2 react with 1 molecule of N 2. What would happen if 3 molecules H 2 reacted with 2 molecules of N 2 ? Would it make more than 2 molecules of NH 3 ? NO!! All 3 of H 2 is used up when it reacts with 1 of N 2. This reaction will make 2 of NH 3 and have 1 N 2 left over. This is called a limiting reagent reaction b/c it determines the amount of product that can be formed. The reaction occurs only until the limiting reagent is used up.

6. Ex.1 2 Na + Cl 2 2 NaCl Determine each of the following if 6.70 moles of Na reacts with 3.80 moles of Cl 2. a) What is the limiting reagent? b) How many moles of NaCl are produced? c) How much excess reagent is leftover?