Oxidation-Reduction Reactions Balancing Redox reactions in Acidic solutions.

Learn how to balance redox reactions in acidic solutions. There are ten guidelines to balancing redox reactions in acidic solutions

Balance FeO (aq) + Al (s)  Fe (s) + Al2O3 (aq) There are nine guidelines to balancing redox reactions in acidic solutions

Guideline #1: Separate reaction into half-reactions. Identify what is being oxidized and reduced and write the half-reactions. Ex. FeO (aq) + Al (s)  Fe (s) + Al2O3 (aq) Fe: reduced, goes from +2 to 0 O: Neither, it remains -2 Al: oxidized, goes from 0 to +3 FeO  Fe Al  Al2O3

Guideline #2: Balance all elements except hydrogen and oxygen Balance elements, except hydrogen and oxygen, in each half reaction. FeO  Fe Al  Al2O3 2Al  Al2O3

Add water to balance oxygen in each half reaction. Guideline #3: Add water. Add water to balance oxygen in each half reaction. FeO  Fe FeO  Fe + H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3

Guideline #4: Add Hydrogen ions. Add hydrogen ions to balance hydrogens in each half reaction. FeO  Fe FeO  Fe + H2O 2H+ + FeO  Fe + H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3 3H2O + 2Al  Al2O3 + 6H+

Guideline #5: Add electrons. Add electrons to balance charges in the half-reactions. FeO  Fe FeO  Fe + H2O 2H+ + FeO  Fe + H2O 2e- + 2H+ + FeO  Fe + H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3 3H2O + 2Al  Al2O3 + 6H+ 3H2O + 2Al  Al2O3 + 6H+ +6e-

Guideline #6: Equal out electrons. Multiply half-reactions by whole numbers to equal electrons. FeO  Fe FeO  Fe + H2O 2H+ + FeO  Fe + H2O 2e- + 2H+ + FeO  Fe + H2O 6e- + 6H+ + 3FeO  3Fe + 3H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3 3H2O + 2Al  Al2O3 + 6H+ 3H2O + 2Al  Al2O3 + 6H+ +6e-

Guideline #7: Add the two half-reactions. Add reactants with reactants, products with products. 6e- + 6H+ + 3FeO +3H2O + 2Al  3Fe + 3H2O + Al2O3 + 6H+ +6e- FeO  Fe FeO  Fe + H2O 2H+ + FeO  Fe + H2O 2e- + 2H+ + FeO  Fe + H2O 6e- + 6H+ + 3FeO  3Fe + 3H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3 3H2O + 2Al  Al2O3 + 6H+ 3H2O + 2Al  Al2O3 + 6H+ +6e-

Guideline #8: Cancel common reactants and products. Cancel reactants and products that show up on both sides of the yield sign. 6e- + 6H+ + 3FeO +3H2O + 2Al  3Fe + 3H2O + Al2O3 + 6H+ + 6e- FeO  Fe FeO  Fe + H2O 2H+ + FeO  Fe + H2O 2e- + 2H+ + FeO  Fe + H2O 6e- + 6H+ + 3FeO  3Fe + 3H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3 3H2O + 2Al  Al2O3 + 6H+ 3H2O + 2Al  Al2O3 + 6H+ +6e-

Guideline #9: Rewrite Balanced Equation. Rewrite the Balanced Chemical Equation and box in the answer. 6e- + 6H+ + 3FeO +3H2O + 2Al  3Fe + 3H2O + Al2O3 + 6H+ + 6e- 3FeO (aq) + 2Al (s)  3Fe (s)+ Al2O3 (aq) FeO  Fe FeO  Fe + H2O 2H+ + FeO  Fe + H2O 2e- + 2H+ + FeO  Fe + H2O 6e- + 6H+ + 3FeO  3Fe + 3H2O Al  Al2O3 2Al  Al2O3 3H2O + 2Al  Al2O3 3H2O + 2Al  Al2O3 + 6H+ 3H2O + 2Al  Al2O3 + 6H+ +6e-

Practice Follow the steps. Realize that the practice is to help with the steps and sometimes demonstrate when steps may not be needed. Practice is to reinforce the guidelines, and may be easier than problems on a quiz or assessment.

Practice #1: H2 (g) + F2 (g)  HF (g)

Practice #2: Fe (s) + CuSO4 (aq)  Cu (s) + Fe2(SO4)3 (aq)

Practice #3: Mn+2 (aq) + NaBiO3 (s)  Bi+3 (aq) + MnO4-1 (aq) Mn+2 (aq) + NaBiO3 (aq)  Bi+3 (aq) + MnO4-1 (aq)