Transcript D - E. R. Greenman

Chemistry Chapter 19 D
Defined: branch of chemistry that
deals with electricity-related redox
reactions
 Electrochemical cell:

◦ System of electrodes and electrolytes that
produces an electric current
◦ System of electrodes and electrolytes that
causes chemical change as current moves

Electrode

Half-cell

Cathode

Anode
◦ Conductor used to make electrical contact
with a nonmetallic part of a circuit
◦ Single electrode immersed in a solution of
its ions
◦ Electrode where reduction takes place
◦ Electrode where oxidation takes place

Electrochemical cell in which redox
takes place naturally and produces a
current
◦ Cations are reduced at the cathode
◦ Anions are oxidized at the anode
◦ Electrons given up at anode are
passed on external connecting wire
to cathode (current flows)

Zinc-carbon dry cell (dry cell battery)
◦ Zinc can is anode
 Zn(s) -> Zn2+(aq) + 2e◦ Carbon rod is cathode
 2NH4+(aq) + 2MnO2(s) + 2e- -> Mn2O3(s) + H2O(l)
+ 2NH3(aq)

Alkaline Battery
◦ Smaller, less corroding effect on container
◦ Anode is zinc
 Zn(s) + 2OH-(aq)  Zn(OH)2(s) + 2e◦ Cathode is carbon or carbon alloy
 2MnO2(s) + H2O(l) + 2e-  Mn2O3(s) +
2OH-(aq)

Mercury Battery
◦ Have large storage capacity, long shelf
life, stable voltage output
◦ Contain toxic materials
◦ Anode is zinc
 Zn(s) + 2OH-(aq) -> Zn(OH)2(s) + 2e◦ Cathode is HgO/graphite alloy
 HgO(s) + H2O(l) + 2e-  Hg(l) + 2OH-(aq)

Read pages 606-610