Chapter 8: Electrochemistry

Electrochemistry

• Deals with the interconversion of electrical energy and chemical energy.

• Studies oxidation-reduction reactions

Redox (oxidation-reduction) reactions

• energy produced from a spontaneous reaction is transformed into electricity

  or

• electricity is used to cause a non-spontaneous chemical reaction (electrolysis).

Electric Charge

Charge on a Proton

Electric Current

• Movement of Charge

• Rate of energy flow

Electric Potential

• Force trying to move the charge

• Ability of electrical field to do work on the charge

Electric Circuit

Path where the electric current flows

Electric Field

Force acting upon other charges in the vicinity

Oxidation

LOSS of electrons

Reduction

GAIN of electrons

Electrochemical reactions

Frequently occur in solutions, which could be acidic, basic, or neutra

Galvanic Cell / Voltaic Cell

Experimental apparatus for generating electricity through a spontaneous reaction.

Luigi Galvani and Alessandro Volta

Galvanic cell is named after Italian scientists ____ and ____.

difference

An electric current flows from the anode to the cathode because there is a ______ in the electrical potential energy between the electrodes

Anode

• Negative or reducing electrode.

• Releases electrons to external circuit.

• Oxidizes during electrochemical reaction.

Cathode

• Positive or oxidizing electrode

• Gains electrons from external circuit.

• Reduces during electrochemical process

Voltmeter

Measures the difference in electrical potential between anode and cathode.

Cell Voltage

Voltage across the electrodes of a galvanic cell.

Electromotive force or emf (ɛ)

• Common term for cell voltage

• Measure of voltage despite the name.

Battery

• A galvanic cell / series of combined galvanic cells

• can be used as a source of direct electric current at a constant voltage

Types of Batteries

1. Dry Cell

2. Mercury

3. Lead Storage

4. Lithium-Ion

5. Fuel

Dry cell

• No fluid component

• Most common dry cell: Leclanché cell

• Used in flashlights and transistor radios

Mercury battery

• Contained in a stainless steel cylinder

• Used in medicine and electronic industries

• More expensive than common dry cell

Lead storage battery

• Consists of 6 identical cells in series

• Commonly used in automobiles

Lithium-Ion battery

• Can be recharged hundreds of times without deterioration.

• Ideal for use in cellular phones, digital cameras, and laptop computers.

Fuel Cells

• Requires a continuous supply of reactant to keep functioning

• Fossil fuel to electrical energy (highly insufficient process)

Corrosion

• Deterioration of metals by electrochemical process.

• Causes damage to buildings, bridges, ships, and cars

ex. rust in iron, tarnish on silver, blue-green patina that develops on copper

Electrolysis

Electrical energy is used to cause a non spontaneous chemical reaction

Electrolytic cell

Apparatus for carrying out electrolysis.

Electrolysis of water

Water in a beaker under atmospheric conditions (1 atm and 25℃) will not spontaneously decompose to form hydrogen and oxygen.