Electrochemistry

Lesson

Part 1 — getting electricity out of a chemical reaction, and measuring how strongly it wants to happen.

In this lesson you will

Describe a galvanic cell, write its cell notation and identify the anode and cathode
Use standard electrode potentials to calculate standard cell EMF and predict whether a reaction is feasible
Apply the Nernst equation to electrodes and cells at 298 K
Relate cell EMF to the Gibbs energy change and the equilibrium constant

Concept

Two kinds of electrochemical cell

In a galvanic (voltaic) cell a spontaneous redox reaction produces electricity. In an electrolytic cell electrical energy drives a non-spontaneous reaction. In both, oxidation occurs at the anode and reduction at the cathode.

Table comparing galvanic and electrolytic cells: energy change, reaction, sign and process at each electrode, and examples
	Galvanic cell	Electrolytic cell
Energy change	Chemical → electrical	Electrical → chemical
Reaction	Spontaneous	Non-spontaneous, driven by a battery
Anode	Negative; oxidation	Positive; oxidation
Cathode	Positive; reduction	Negative; reduction
Example	Daniell cell, dry cell	Electroplating, refining copper

Diagram

The Daniell cell

Zinc is the anode (oxidation, negative); copper is the cathode (reduction, positive).

Zinc in zinc sulfate solution and copper in copper sulfate solution are joined by a wire and a salt bridge. The voltmeter reads about 1.1 V when the solutions are 1 M.

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