1. Section 3.3 Stoichiometry and Chemical Reactions

2. In this section: a. Chemical reactions and equations b. Balancing equations c. Reaction stoichiometry

3. Chemical reactions and equations Reactants Products CH 3 CHCH 2 + HCl CH 3 CHClCH 3

4. Chemical equation: before and after Mechanism: how you get there Step 1. Step 2.

5. The most important thing: It’s the same atoms Reactants Products CH 3 CHCH 2 + HCl CH 3 CHClCH 3

6. The Law of Conservation of Matter It’s the same atoms Stoichiometric Coefficients: CH 3 CHCH 2 + HCl CH 3 CHClCH 3 C 2 H 2 + 2 H 2 CH 3

7. Balancing Chemical Equations Goal: same number of atoms of each element on both sides Rule: you can change stoichiometry coefficients, not the molecular formulas CH 4 + O 2 CO 2 + H 2 O

8. A bit harder C 4 H 10 + O 2 CO 2 + H 2 O Another Example: Mg + O 2 MgO

9. Big misconception: stoichiometric coefficients are NOT how much reacts/forms CH 4 + 2 O 2 CO 2 + 2 H 2 O

10. Balancing Equation = mol to mol conversion factor CH 4 + 2 O 2 CO 2 + 2 H 2 O

11. Amounts tables: If 0.46 mol O 2 react, how much CO 2 and H 2 O are formed, and how much CH 4 reacts? CH 4 + 2 O 2 CO 2 + 2 H 2 O change:

12. Real experiments use mass, not moles. gram gram conversions Path: grams A moles A moles B grams B

13. CH 4 + 2 O 2 CO 2 + 2 H 2 O 25.0 g of O 2 react. What mass of CH 4 reacts and what masses of CO 2 and H 2 O are formed?

14. CH 4 + 2 O 2 CO 2 + 2 H 2 O 25.0 g of O 2 react. What mass of CH 4 reacts and what masses of CO 2 and H 2 O are formed?