Chapter 3 Molecules, Compounds, & Chemical Equations

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 #4 RRPP 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: A2 + B2→ A2B unbalanced 2 A2 + B2→2 A2B balanced

9. Balancing Chemical Equations

10. Balancing Chemical Equations

15. Balancing Chemical Equations • 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 + O2→ Al2O3 Al + Br2→ AlBr3

17. Balancing Chemical Equations • Decomposition (AB → A + B) • Heat usually required (Δ means heat) • Exact opposite of synthesis Practice Problem Δ KClO3→ KCl + O2

18. Balancing Chemical Equations • Single Replacement (A + BC → AC + B) Yet more practice. Al + H2SO4→ H2 + Al2(SO4)3

19. Balancing Chemical Equations • Double Replacement (AB + CD → AD + CB) • Also called a Metathesis Reaction Try this one now FeCl3 + NH4OH → Fe(OH)3 + NH4Cl