1. Chemistry Chapter 19 D

2.  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

3.  Electrode ◦ Conductor used to make electrical contact with a nonmetallic part of a circuit  Half-cell ◦ Single electrode immersed in a solution of its ions  Cathode ◦ Electrode where reduction takes place  Anode ◦ Electrode where oxidation takes place

4.  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)

6.  Zinc-carbon dry cell (dry cell battery) ◦ Zinc can is anode  Zn (s) -> Zn 2+ (aq) + 2e - ◦ Carbon rod is cathode  2NH 4 + (aq) + 2MnO 2(s) + 2e - -> Mn 2 O 3(s) + H 2 O (l) + 2NH 3(aq)

8.  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  2MnO 2(s) + H 2 O (l) + 2e -  Mn 2 O 3(s) + 2OH - (aq)

9.  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) + H 2 O (l) + 2e-  Hg (l) + 2OH- (aq)

10.  Read pages 606-610