UNIT 7: Lesson 1: Introduction

The Electrochemical Cell An electrochemical cell is a system that produces electrical energy from chemical energy. Each half of the electrochemical cell is called a half-cell. The reaction that occurs in a half-cell is called a half-reaction. This is just a brief intro – we will learn much more about electrochemical cells next unit, but first we must learn some theory...

Redox Reactions An oxidation reaction is a half-reaction in which a species loses electrons. A reduction reaction is a half-reaction in which a species gains electrons. Just remember: LEO the lion says GER! These two reactions always go hand-in-hand. The overall reaction involving the loss and gain of electrons is called a redox reaction.

Oxidation or Reduction? A species being oxidized becomes more positively charged. (LEO → less negative = more positive.) E.g. Zn → Zn2+ + 2 e-. A species being reduced becomes more negatively charged. (GER → more negative = less positive.) E.g. Cu2+ + 2 e- → Cu.

Brain Break! Spot It!

Oxidizing and Reducing Agents In the redox reaction 2 Ag+ + Cu → 2 Ag + Cu2+ Ag+ is the “agent” that causes Cu to be oxidized, so Ag+ is the oxidizing agent. Cu is the “agent” that causes Ag+ to be reduced, so Cu is the reducing agent. The oxidizing agent is reduced, and the reducing agent is oxidized! Note: the reducing or oxidizing agent is the entire molecule, not just the atom.

Demo: Cereal Surprise! Predict: What chemical can be easily extracted from breakfast cereal? Observe: What did you see? Explain: Iron metal (Fe) is put into cereal to react with the hydrochloric acid in our stomachs and provide the nutrient Fe2+: Fe + 2 HCl → Fe2+ + 2 Cl- + H2 Is the iron reduced or oxidized in the stomach? Demo 12.V.2 – 15 min

Practice: Pg. 192 #1 and 2 15 min