1 / 14

Half-reactions show the oxidation or reduction reaction separated.

Half-reactions show the oxidation or reduction reaction separated. +1. +2. 0. 0. Cu (s) + 2 AgNO 3(aq) → Cu(NO 3 ) 2(aq) + 2 Ag (s). Oxidation : Cu → Cu 2+ + 2e –. Reduction : Ag + + 1e – → Ag.

neci
Download Presentation

Half-reactions show the oxidation or reduction reaction separated.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Half-reactions show the oxidation or reduction reaction separated. +1 +2 0 0 Cu(s) + 2 AgNO3(aq) → Cu(NO3)2(aq) + 2 Ag(s) Oxidation: Cu → Cu2+ + 2e– Reduction: Ag+ + 1e– → Ag Half reactions are often shown as aqueous net ionic equations – spectator IONS not included.

  2. Balancing redox reactions 2

  3. Two methods for balancing redox reactions: Oxidation number method Half-reaction method. • Balance redox equations using the oxidation • number method. • Balance redox equations in acidic and basic • solutions using the half reaction method.

  4. Redox reactions usually require an acidic or basic solution. • Acid / base not oxidized or reduced in reaction. • Usually converted to water. • Half-reaction method is used for balancing redox reactions in the presence of acid or base.

  5. Balancing Redox Reactions in Acidic Solutions -2 +6 -2 +4 +3 -2 +6 Cr2O72–(aq) + SO32–(aq) → Cr3+(aq) + SO42–(aq) 1: Assign ox.numbers and write half-reactions. Oxidation: SO32- → SO42- + 2e– Reduction: Cr2O72- + 3e– → Cr3+ Not ionic (no spectators) –keep together!

  6. 2: Balance all elements except H and O. Oxidation: SO32- → SO42- + 2e– Reduction: Cr2O72- + 6e– → Cr3+ 2 3: Balance oxygen atoms by using H2O. Oxidation: SO32- + H2O → SO42- + 2e– Reduction: Cr2O72- + 6e– → 2 Cr3+ + 7 H2O

  7. 4: Balance hydrogen atoms using H+ions. Oxidation: SO32- + H2O → SO42- + 2e– +2 H+ Reduction: Cr2O72- + 6e– → 2 Cr3+ + 7 H2O 14 H+ + 5: Balance the number of electrons lost and gained. Oxidation: 3 x (SO32- + H2O → SO42- + 2e– +2 H+) 3 SO32- + 3 H2O → 3 SO42- + 6e– +6 H+ Reduction: 14 H+ + Cr2O72- + 6e– → 2 Cr3+ + 7 H2O

  8. 6: Add the two half-reactions. Oxidation: 3 SO32- + 3 H2O → 3 SO42- + 6e– +6 H+ Reduction: 14 H+ + Cr2O72- + 6e– → 2 Cr3+ + 7 H2O 8 H+ + Cr2O72- + 3 SO32- → 2 Cr3+ + 3 SO42- + 4 H2O

  9. Balance the following reaction in a acidic solution. -1 +7 0 +4 MnO4– + I– → MnO2 + I2 3 x ( ) 2 Oxidation: I1- → I2 + 2e– 2x ( ) 4 H+ + Reduction: MnO41- + 3e– → MnO2 + 2 H2O Oxidation: 6 I1- → 3 I2 + 6e– Reduction: 8 H+ + 2 MnO41- + 6e– → 2 MnO2 + 4 H2O 8 H+ + 2 MnO4– + 6 I– → 2 MnO2 + 3 I2 + 4 H2O

  10. Balancing Redox Reactions in Basic Solutions • For basic solutions add hydroxide ions. +3 +4 +4 +7 MnO4– + C2O42– → CO2 + MnO2 2 Oxidation: C2O42- → CO2 + 2e– 4 H+ + + 2 H2O Reduction: MnO41- + 3e– → MnO2 *5a: Add the same number of OH- as H+ to BOTH sides of the equation.

  11. Oxidation C2O42- → 2 CO2 + 2e– 4 H2O 2 Reduction: 4 H+ + MnO41- + 3e– → MnO2 + 2 H2O 4 OH- + + 4 OH- 5b: Eliminate H+ / OH- by forming water.. Cancel any waters you can to simplify each half reaction. OxidationC2O42- → 2 CO2 + 2e– 3 x ( ) 2x ( ) Reduction: 2 H2O + MnO41- + 3e– → MnO2 + 4 OH-

  12. Oxidation3 C2O42- → 6 CO2 + 6e– Reduction: 4 H2O + 2 MnO41- + 6e– → 2 MnO2 + 8 OH- 4 H2O + 2 MnO4– + 3 C2O42– → 2 MnO2 + 6 CO2 + 8 OH–

  13. Balance the following reaction in a basic solution. +1 +1 +3 -1 N2O + ClO– → NO2– + Cl– 3 H2O + 2 Oxidation: N2O → NO2- + 4e– + 6 H+ 2 H+ + + 1 H2O Reduction: ClO- + 2e– → Cl- 5a: Add same number of OH- to BOTH side. 5b:Cancel any waters you can to simplify half reactions.

  14. 6 H2O 3 Oxidation: N2O → NO2- + 4e– 6 OH- + 3 H2O + 2 + 6 OH- + 6 H+ Reduction: ClO- + 2e– → Cl- + 2 OH- 2 OH- + + 1 H2O 2 H+ + 2 H2O 1 2 1 Oxidation: N2O → NO2- + 4e– 6 OH- + 2 + 3 H2O Reduction: ClO- + 2e– → Cl- 2x ( ) + 2 OH- 1 H2O + 2 H2O + 2 ClO- + 4e– → 2 Cl- +4 OH- 2 OH– + 2 ClO– + N2O → 2 Cl– + 2 NO2– + H2O

More Related