Redox and Electrochemistry Adapted from Addison Wesley Chemistry and other Chemistry resources Part I

Redox Oxidation: Lose Electrons Oxidation (LEO), electron donor or reducing agent Reduction: Gain Electrons Reduction (GER), electron acceptor or oxidizing agent Remember electrons, e-, have a negative charge so LEO will become more positive from reactant to product, and GER will become more negative from reactant to product.

Using single replacement reactions to learn REDOX Using the activity series, if the single element is more active than the element being replaced in compound form, a single replacement reaction will occur. Metal will replace metal, or non-metal will replace non-metal, so determine what you have. Li + NaCl will react because Lithium metal is more active than Sodium metal, so the metals will switch places Li + NaCl  Na + LiCl

Ions Li + NaCl  Na + LiCl Create an ionic equation Cl- is a spectator ion, because the change took place with the two metals. It is the same on both sides of the equation, so it may be taken out of the equation. Li + Na+  Na + Li+

Now redox and Half Reactions Li + Na+  Na + Li+ Separate the elements into half reactions Li  Li+ for lithium Na+  Na for sodium Neutralize the side of the equation needed with electrons Li  Li+ + 1 e- Na+ + 1 e-  Na

Redox, electroChemistry Li  Li+ + 1 e- ; Lithium has lost 1 electron from reactant to product (LEO) Na+ + 1 e-  Na ; Sodium has gained 1 electron from reactant to product (GER) Redox causes an electrical current if utilized in a galvanic cell The flow of electrons will always move from the more active element to the less active element in a circuit…. If spontaneous.

Balancing equations with electrons using Half reactions Li + MgCl2  Mg + LiCl : not balanced Write unbalanced equation in ionic form Li + Mg+2 + Cl-  Mg + Li+ + Cl- Separate half reactions into elements, then balance atoms….i.e. oxidation and reduction. Li Li+ Mg+2 Mg

Balancing Continued Add electrons to each half reaction Balance the electrons of both half reactions [ Li Li+ + 1 e- ] x 2 = 2 Li  2 Li+ + 2 e-’s (LEO) Mg+2 + 2 e-’s  Mg (GER) The more active metal will lose electrons…LEO The less active metal will gain electrons….. GER

2 Li + MgCl2  Mg + 2 LiCl The flow of electrons moves from more active metals to less active metals in a spontaneous reaction. Electrons will flow from lithium to magnesium