When we studied chemical reactions, we learned about oxidation and reduction. Electrochemistry is all about redox reactions so we will begin by reviewing these concepts.

**Learning Objectives**

- Identify oxidation, reduction, oxidizing agent, and reducing agent in a chemical equation. (20.1)
- Complete and balance redox equations using the method of half-reactions. (20.2)

To become familiar with the topics presented in this mission, view the slides below and take note of the key ideas. These are from sections 20.1-20.2 of your text.

Now work through practice problems 20.1-20.3, and post your work to OneNote.

Work through these mastery problems and post your work to OneNote. The key is available on OneNote also.

For each of the following reactions write two separate half-reactions, one showing oxidation and one showing reduction, and then use the half-reactions to balance the full redox equation.

(a) Na + Cl_{2} → NaCl

Oxidation:

Reduction:

Full Equation:

(b) Mg + O_{2} → MgO

Oxidation:

Reduction:

Full Equation:

(c) BrO^{–} → BrO_{3}^{–} + Br^{–}

Oxidation:

Reduction:

Full Equation:

(d) Zn + FeSO_{4} → ZnSO_{4} + Fe

Oxidation:

Reduction:

Full Equation:

**20.93 **A *disproportionation* reaction is an oxidation–reduction reaction in which the same substance is oxidized and reduced. Complete and balance the following disproportionation reactions:

- Ni
^{+}(*aq*) → Ni^{2+}(*aq*) + Ni(*s*) (acidic solution) - MnO
_{4}^{2–}(*aq*) → MnO_{4}^{–}(*aq*) + MnO_{2}(*s*) (acidic solution) - H
_{2}SO_{3}(*aq*) → S(*s*) + HSO_{4}^{–}(*aq*) (acidic solution) - Cl
_{2}(*aq*) → Cl^{–}(*aq*) + ClO^{–}(*aq*) (basic solution)

** **

Redox isn't that bad when you take the time to break it down. Now let's move on and see how this applies to batteries!