1. STUDY GROUPS- FIRST MEETING THIS WEEK EXAM #1 THIS WEEK! FRIDAY, SEPTEMBER 18 TH Addition to Study Guide: Given the masses of two reactants and a chemical equation, be able to determine e which is the limiting reactant (Chemical Analysis is not on the exam) Announcements

2. Alum Lab- % Yield Calculation

3. Limiting Reactants 2H 2 + O 2  2H 2 O Example: We have 10 mol H 2 and 7 mol O 2 What is the number of moles of O 2 needed to react with all of the H 2 ? How much O 2 will be left over? 7 mol O 2 available- 5 mol O 2 needed= 2 mol O 2

4. Limiting Reactants 2H 2 + O 2  2H 2 O Example: We have 10 mol H 2 and 7 mol O 2

5. Limiting Reactants If given the amount of starting materials, how do I determine which is the limiting reactant? Two approaches: 1. Determine the theoretical yield from each 2. Divide the # moles of each by its stoichiometric # (In both approaches, the smaller # is the limiting reactant)

6. Example The reaction: We have 5.0 mol SO 2, 4.o mol O 2, and 10.0 mol H 2 O. Which is the limiting reactant? What if I started with 5g SO 2, 4g O 2, and 10g H 2 O?

7. Stoichiometry- Limiting Reactants 100mL 0.1M HCl + coil of Mg in each flask  Flask 1= 1.2g Mg  Flask 2= 0.6g Mg  Flask 3= 2.4g Mg The reaction: Which balloon inflates the most? Least? Does half the Mg mean half the H 2 ? Does twice the Mg mean twice the H 2 ?