Balancing Chemical Equations Homework 3-1 Balancing Chemical Equations Video link

Example: Level 1 Balancing Problem K + Br2 → KBr Atomic Level Picture: K = Br = Atom Count: K: Br: → K: Br: 1 2 1 1

Example: Level 1 Balancing Problem K + Br2 → 2 KBr Atomic Level Picture: K = Br = Atom Count: K: Br: → K: Br: 1 2 2 2

Example: Level 1 Balancing Problem 2 K + Br2 → 2 KBr Atomic Level Picture: K = Br = Atom Count: K: Br: → K: Br: 2 2 2 2

Level 1 Practice: Balance the following reactions: 2 2 1) Mg + O2 → MgO 2) Na3N → Na + N2 3) Al + MgO → Mg + Al2O3   2 6 2 3 3

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 1 1 3 1 1 2 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 1 1 3 1 1 2 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 2 1 3 1 1 2 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 2 2 3 1 1 2 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 2 2 6 1 1 2 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 3 2 2 6 1 1 2 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 3 2 2 6 1 1 6 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 2 3 2 2 6 1 1 6 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 2 3 2 2 6 2 1 6 6

Level 2: Helpful hint: Least Common Multiple: Example: KClO3 → KCl + O2   K: Cl: O: → K: Cl: O: Problem: 2 O on right will not divide evenly into 3 O on left. What is the least common multiple of 2 and 3? 2 2 3 2 2 6 2 2 6 6

Level 2: Practice 4) Al + O2 → Al2O3 5) Al + HCl → AlCl 3 + H2 4 3 2 3   5) Al + HCl → AlCl 3 + H2 4 3 2 3 3

Level 2: Practice 4) Al + O2 → Al2O3 5) Al + HCl → AlCl 3 + H2 4 3 2 2   5) Al + HCl → AlCl 3 + H2 4 3 2 2 6 2 3

Level: Complex problems Level 3: Most complex problems have elements that appear in multiple terms on each side and/or issues with odd / even. Hints: Balance elements that appear in only 1 term on each side first. Remember that if the subscript for an element term on one side is an even # and is odd in one term on the other side, doubling odd #’s is the easiest way to convert odd #’s to even #’s.

Example #1: C H O CH4 + O2 → CO2 + H2O Start with or because those elements appear in only 1 term on both sides. Save for last because it appears in multiple terms and would require filling in 3 coefficients simultaneously which is more complex. C H O

Example #1: C H O CH4 + O2 → CO2 + 2 H2O Start with or because those elements appear in only 1 term on both sides. Save for last because it appears in multiple terms and would require filling in 3 coefficients simultaneously which is more complex. C H O

Example #1: C H O CH4 + 2 O2 → CO2 + 2 H2O Start with or because those elements appear in only 1 term on both sides. Save for last because it appears in multiple terms and would require filling in 3 coefficients simultaneously which is more complex. C H O

Practice C: H: O: C: H: O: 6) C6H12O6 → C2H6O + CO2 2 2 4 +1 2 2 +2 4 2+1 6 1+2 3 3 6 5 12 6 4

7) C5H12 + O2 → CO2 + H2O C: H: O: C: H: O: 8 5 6 10+1 6 5 12 2 1 2 2+1 16 5 12 16 11

3 8) C2H5OH + O2 → CO2 + H2O 2 3 C: H: O: C: H: O: 3 4 +1 2 6 1+2 1 2 2 +1 3 2 6 5 3 7

Odd-even: H2O2 → H2O + O2 2 2 Example #1: H: 2 O: 2 H: 2 O: 1 + 2 2 4

Odd/Even Example #2: C4H10 + O2 → CO2 + H2O 10 8 2 13 4 5 C: H: O: C: H: O: 10 8 2 13 4 5 10 16 4 8 5 10 4 10 2 1 2 2 + 1 13 8 20 26 8 20 26

9) C8H18 + O2 → CO2 + H2O   10) NH3 + NO → N2 + H2O

9) 2 C8H18 + 25 O2 →16 CO2 + 18 H2O   10) NH3 + NO → N2 + H2O

9) 2 C8H18 + 25 O2 →16 CO2 + 18 H2O   10) 4 NH3 + 6 NO → 5 N2 + 6 H2O