20-2 Batteries

A battery is a group of cells in a series...the total charge is the sum of the charges of the cells.

D,C,AA, AAA and other similar products are cells, not batteries.

Dry Cells

AAA,AA,C,D and other similar cells are dry cells. They have a graphite cathode and a zinc anode. They are called dry-cells because they have a

paste for electrolyte instead of liquid.

Primary and Secondary Batteries

A primary battery has redox reactions that are not easily reversed. They are not rechargeable.

Secondary batteries are also called storage or rechargeable batteries because they hold a charge and can be recharged over and over.

Lead-Acid Storage Battery

The 12 V battery in your vehicle is a lead-acid storage battery.

It has the discharge reaction below:

anode cathode electrolyte

Pb(s)

+ PbO2(s)

+ H2SO

4(aq) → PbSO

4(aq)+ 2H

2O

(l)+

Lithium Cells

Lithium has the lowest reduction potential. Use of lithium in a cell allows it to produce

greater voltage than zinc..(by 2.3V)

Fuel Cells

A fuel cell has an electrolyte solution that can be added or renewed to give a new recharge.

Fuel cells are used in space and in some vehicles, but they are expensive.

Corrosion

Corrosion is the loss, or oxidation, of metal through redox reactions.

Corrosion can be slowed by painting or coating metals, or by covering them with metals that are less prone to corrode.

Galvanization is coating metal with zinc. Attaching a metal that is more prone to oxidize

causes redox reactions to shift to the sacrificial metal instead of the main metal of a structure.

20-3 Electrolytic Cells and Processes

Electrolytic processes use electricity to make chemical changes.

Electrolysis is an electrolytic process.

Electroplating is an electrolytic process.

Electrolytic Cell (Electroplating) Start by drawing a battery or power supply. Hang the item to be plated on the – electrode...

called the cathode and where reduction occurs. The metal to be plated is hung from the + electrode

of the battery, called the anode where oxidation occurs.

Both the oxidation and reduction half-reactions involve the plating metal...silver here.