Chemistry: Production of Materials
Batteries: Batteries are very important in our modern world as they provide a portable source of
electrical energy. A battery may consist of one galvanic cell or a number of cells joined in a series.
The dry cell: The dry cell (or Leclanche’ cell) is one of the
most common and reliable sources of portable electoral
power. The image to the left shows the typical structure of
a dry cell. The central positive cathode consists of an inert
graphite rod surrounded by graphite and manganese
dioxide powder. The negative anode consists of the zinc
casing of the cell.
The chemistry of the dry cell and issues related to its cost
and practicality, as well as its effect on society and the
environment, are summarised below.
Dry Cell Feature
Voltage
Comment
1.5 V
Anode (-)
Zn casing
Cathode (+)
MnO₂, C
Electrolyte
Aqueous paste of ammonium chloride 26% (w/w)
Other Information
Cost and Practicality
Effects on Society
Effects on the
Environment
The MnO₂ ensures that hydrogen atoms released from the ammonium
ions during reduction are converted into water. The ammonia that forms
at the cathode complexes with the zinc ions to form a stable complex ion.
The materials of the cell are inexpensive and cheap to replace. The cells
have a low energy density. The voltage falls during use, due to a drop in
electrolyte concentration around the cathode.
The cells have short shelf life as the zinc is attacked by the ammonium
chloride.
Dry cell batteries are used in low drain appliances such as torches, remote
controls, LCD calculators and battery operated toys that do not require
high currents
Battery components are weakly acidic and non-toxic. There are few
environmental consequences on disposal
Thickett, G. (2006) Chemistry 2: HSC course. John Wiley & Sons Australia: QLD
Follow this link for further basic yet useful information on dry cell batteries!
http://www.wisegeek.com/what-is-a-dry-cell-battery.htm#
http://www.youtube.com/watch?v=4l-2NcTbLBY
Thickett, G. (2006) Chemistry 2: HSC course. John Wiley & Sons Australia: QLD