March 19, 2015 Chapter 13: Electrochemical Cells

electrochemical cell: any device that converts chemical energy into electrical energy, or vice versa March 19, 2015 March 19, 2015 Voltaic Cell

-any device that uses a redox reaction to transform chemical potential energy into electrical energy (moving electrons)

-the oxidizing agent and reducing agent are separated -each is contained in a half cell

There are two half cells in a voltaic cell

Cathode Anode -contains the SOA -contains the SRA -reduction reaction -oxidation takes place takes place - (-) electrode -+ electrode -anions migrate -cations migrate towards the anode towards cathode March 19, 2015

Electrons move through an external circuit from the anode to cathode

Electricity is produced by the cell until one of the reactants is used up

Example: A simple voltaic cell March 19, 2015

When designing half cells it is important to note the following:

-each half cell needs an electrolyte and a solid conductor

-the electrode and electrolyte cannot react spontaneously with each other

(sometimes carbon and platinum are used as inert electrodes) March 19, 2015 There are two kinds of porous boundaries 1. Salt Bridge 2. Porous Cup · an unglazed ceramic cup · tube filled with an inert · separates solutions but electrolyte such as NaNO allows ions to pass 3 through or Na2SO4 · the ends are plugged so the solutions are separated, but ions can pass through

Porous boundaries allow for ions to move between two half cells so that charge can be equalized between two half cells

2+ 2– electrolyte: Cu (aq), SO4 (aq) 2+ 2– electrolyte: Zn (aq), SO4 (aq)

electrode: zinc electrode: copper March 19, 2015

Example: Metal/Ion Voltaic Cell V

Co(s)

Zn(s)

Co2+

SO 2- 4

2+ SO 2- Zn 4

Example: A voltaic cell with an inert electrode March 19, 2015

Example Label the cathode, anode, electron movement, ion movement, and write the half reactions taking place at each half cell. Describe one observation that could be made at each half cell that would indicate the cell is functioning. March 19, 2015 March 19, 2015

Draw a diagram of the following cell - 2+ C(s) | I2(aq), I (aq)|| Pb (aq) | Pb(s)