Electrochemistry

Introduced to this in AP Chemistry

Review Oxidation Numbers

Separating the oxidation & reduction reactions allows electron transfer to occur through an external wire

A group of such cells is called a battery

• E${}^{°}$ (volts): Cell voltage, electromotive force (emf), cell potential
• Half reactions are reversible $\to$ oxidation (E${}^{°}$ sign changes)
• Given two half reactions to create a cell - one must be reversed

Zu - Cu Redox Reaction §

From a table of reduction potentials (page A-26):

• Zn${}^{2+}$ + 2e${}^{-}$ $\to$ Zn E${}^{°}$ = -0.76 V
• Cu${}^{2+}$ 2e${}^{-}$ $\to$ Cu E${}^{°}$ = + 0.34 V

reverse and change the sign for the reaction that will give a positive value when combined

• Ox: Zn $\to$ Zn${}^{2+}$ + $\cancel{2e^{-}}$ E${}^{°}$ = + 0.76 V
• Red: Cu${}^{2+}$ + $\cancel{2e^{-}}$ $\to$ Cu E${}^{°}$ = + 0.34 V Zn + Cu${}^{2+}$ $\to$ Zn${}^{2+}$ + Cu E${}^{°}$ = + 1.10 V

• Anode: electrode where oxidation occurs
• Cathode: electrode where reduction occurs