1. Chapter 3 Molecules, Compounds, & Chemical Equations CHE 123: General Chemistry I Dr. Jerome Williams, Ph.D. Saint Leo University

2. Overview Balancing Chemical Reactions

3. Chemical Reactions Parts of a Chemical Reaction(R → P) – Reactants are found on the left side – Products are found on the right side – Arrow means “yields”, “produces”, “reacts to form”, etc. – Remember basic format using Axiom #4

4. Chemical Reactions Axiom #4RRPP Principle Reactants React with one another so that Products are Produced.

5. Chemical Reactions Revisited Components of a Chemical Reaction – Reactants – Arrow(“yields” or “produces” ) – Products – Physical States (s) = solid (l) = liquid (g) = gas (aq) = aqueous (dissolved in water) – Reaction Conditions

7. Balancing Chemical Equations The changes that matter undergo are at the heart of chemistry. Chemical Reactions are a result of reactant atoms rearranging to form products. All chemical reactions must be balanced so as to obey the law of conservation of matter (mass).

8. Balancing Chemical Equations Reactions are balanced using coefficients. Example: A 2 + B 2 → A 2 Bunbalanced 2 A 2 + B 2 → 2 A 2 Bbalanced

9. Balancing Chemical Equations

15. Four General Classes of Reactions – Synthesis – Decomposition – Single Replacement – Double Replacement (Metathesis)

16. Balancing Chemical Equations Synthesis(A + B → AB) Try these for practice Al +O 2 →Al 2 O 3 Al +Br 2 →AlBr 3

17. Balancing Chemical Equations Decomposition(AB → A + B) – Heat usually required(Δ means heat) – Exact opposite of synthesis Practice Problem Δ KClO 3 →KCl+O 2

18. Balancing Chemical Equations Single Replacement(A + BC → AC + B) Yet more practice. Al +H 2 SO 4 →H 2 + Al 2 (SO 4 ) 3

19. Balancing Chemical Equations Double Replacement (AB + CD → AD + CB) – Also called a Metathesis Reaction Try this one now FeCl 3 + NH 4 OH →Fe(OH) 3 + NH 4 Cl