Electrochemistry

Electrochemistry, in a sense, is electron movement. The study of electrochemistry is what makes the computer/tablet/phone you are looking at this website possible. Electrochemical reactions are also called redox (reduction-oxidation) reactions. These are reactions in which elements change their oxidation state from the reactants to the products.

Redox Reactions

View these resources to learn how to recognize and balance redox reactions.

Electrochemistry Vocabulary

• In oxidation, elements lose electrons whereas in reduction elements gain electrons (OIL RIG: Oxidation Is Loss; Reduction Is Gain).

• Half-reaction: shows the independent oxidation or reduction reactions

• Electrochemical Cells: we isolate the reduction and the oxidation in separate cells

  • this forces a path that the electrons have to follow

  • these are connected by a salt bridge which completes the circuit but keeps the half-reaction separate

• Potential (𝐸): measure the tendency for a reaction to move towards equilibrium

  • positive potential: spontaneous; favorable; electrons flow from anode to cathode

  • negative potential: electrolytic cell

• Current (𝐼): opposite direction of flow of electron

• Standard Reduction Potential (𝐸∘): the electrode potential compared to a standard (usually the Standard Hydrogen Electrode)

Types of  Electrochemical Cells

Galvanic Cell: proceeds on its own

• favorable or spontaneous reaction

• electrons will flow from anode to cathode

• store energy

• Here is a video that will help (have fun!): “You Start at the Anode” (3:28)

Electrolytic Cell:

• requires external energy to move electrons against potential

• electrons flow from the cathode to the anode

• i.e. recharging a battery

Reversible Cell:

• these cells can act as a galvanic and electrolytic cell

• i.e. car battery

Irreversible Cell:

• can only act as a galvanic cell

• changing direction will cause a different half-reaction to occur

Important Electrochemistry Equations

• • 𝑛 = # of electrons

  • 𝐹: Faraday’s constant

• • Both the cathode and anode standard potentials are used in reduction form (directly from the table)

• 𝐸𝑐𝑒𝑙𝑙 @ equilibrium = 0

• shorthand notation: anode(oxidation) || cathode (reduction)

solid anode | anode (next phase,concentration) || cathode (next phase) | solid cathode

• • | : phase boundary; use every time you change phases

  • || : salt bridge

Problem Solving: Half Cell (~3 minutes)