286 DIY Science: Illustrated Guide to Home Chemistry Experiments
EvdRE y Ay ELECTRoCHEmISTRy- All electric batteries and cells are electrochemical in
nature, from the AA alkaline cells in your flashlight
to the nickel metal hydride (NiMH) battery in your
digital camera to the lead-acid battery in your car. - Many pure gases, such as hydrogen, the oxygen
used in hospitals, and the chlorine used for water
purification and many other purposes, are produced
electrochemically, by passing electric current
through water or an aqueous solution of a salt that
contains the gaseous element in ionic form. - Many commercially important elements, including
aluminum, bromine, chlorine, and sodium, are
produced exclusively or primarily electrochemically. - Commercially important pure forms of many metals,
including copper, silver, gold, and platinum, are
produced electrochemically.
Electrical work is similar to physical work, but instead of the
physical work of moving a box from the floor to a shelf, electrical
work is required to move electrons through a conductor or move
ions through a solution to an electrode. And, just as the position
of the box determines its physical potential energy, the type and
state of charge of ions determine their electric potential energy
(or electric potential for short).
Just as air moves (as wind) from a point of higher air pressure
to a point of lower air pressure, an electric charge moves (as an
electric current) from a point of higher electric pressure to a point
of lower electric pressure. Electric pressure is denominated in
volts, so an electric charge moves from an area at higher voltage
to an area at lower voltage. To determine the electric work needed
to move a charge through a conductor, multiply the charge by the
potential difference:
Charge (C) · potential difference (v) = Electric work (j)
Electric charge is specified in Coulombs (C), the potential
difference in volts (V), and electric work in Joules (J).
In this chapter, we’ll examine both types of electrochemical
processes by using an electric current to initiate and sustain a
chemical reaction, and by using chemical reactions to produce
electric current.