Redox Reactions

Half Reaction One of the two parts of a redox reaction Oxidation Reduction Includes element and electrons involved Example: Fe  Fe3+ + 3e-

Example Write the half reaction for when the element chlorine is converted into the chloride ion.

Example Write the half reaction for when Fe2+ is converted to Fe4+ and state whether it is an oxidation or reduction.

Redox Reactions Oxidation and Reduction Reactions Reaction in which electrons are transferred between atoms Remember: Oxidation is loss of electrons Reduction is gain of electrons

In a chemical reaction, oxidation cannot happen without reduction Pneumonic: LEO the lion says GER. Loss electrons is oxidation, gain of electrons is reduction

Oxidation and Reduction in Redox Reactions Assign oxidation numbers to each element in all compounds and elements Values that change tell you what substance is oxidized and what substance is reduced

Example 2 K + Br2  2 KBr What is the charge of each element in the reaction? What substance is reduced? What substance is oxidized?

Example 3 SnCl4 + 2 Fe  3 SnCl2 + 2 FeCl3 What is the charge of each element in the reaction? What substance is reduced? What substance is oxidized?

Zn(s) + Cu2+ (aq)  Zn2+(aq) + Cu(s) Example: Write the two half reactions that make up this redox process and state which is oxidation and which is reduction: Zn(s) + Cu2+ (aq)  Zn2+(aq) + Cu(s)

Balancing half reactions Write each half reaction including the correct number of electrons gained or lost While combining the two half reactions, make sure that the electrons cancel out Example: Determine the balanced redox reaction between: I2(s) +2e-  2I-(aq) Fe(s) Fe2+(aq) + 2e-

Practice Problem Determine the balanced redox reaction between: Co2+ (s) +2e-  Co(aq) Cr(s)  Cr3+(aq) + 3e-