What does this?

Have to dowith this?

NOTHING!!!

B/ Electrolytic Cells: Electrolysis - when an electric current is used to force a redox reaction that is normally

nonspontaneous to occurThey convert electrical energy chemical energy

Like voltaic cells, electrolytic cells have:a. redox reactions involving electrons

b. an anode where oxidation takes place because electrons are removed (lost) from there

c. a cathode where reduction takes place because electrons are moved (gained) there

d. electrons flowing from anode to cathode

battery+ -

Unlike voltaic cells,electrolytic cells have these differences:a. A battery or other source of electrical energy must be used because the reaction is nonspontaneous.b. The anode is now positive (+), and the cathode is now negative (-). This is the opposite of a voltaic cell.c. Both oxidation and reduction occur in the same cell.

anode cathode

e-

+ -

Diagram of anelectrolytic cell:

e-

Uses of Electrolytic Cells:

Ex. Electrolysis of molten salts to produce active metals:

2NaCl(l) + 2Na(l) + Cl(g)

Oxidation at the anode: 2Cl- Cl2 + 2e-

Reduction at the cathode: 2Na+ + 2e- 2Na

electrical energy

Uses of Electrolytic Cells:

Ex. Electrolysis of molten salts to produce active metals:

2NaCl(l) + 2Na(l) + Cl(g)

Oxidation at the anode: 2Cl- Cl2 + 2e-

Reduction at the cathode: 2Na+ + 2e- 2Na

Ex. The electrolysis of water:

2H2O(l) + 2H2(g) + O2(g)

Notice that twice as many hydrogen molecules as oxygen molecules are produced.

In both examples, electrical energy is a “reactant.”

electrical energy

electrical energy

The half reactionsin the electrolysisof H2O are notas simple as other examplesseen so far:

At the anode: 2H2O O2 + 4H+ + 4e-

At the cathode: 4H+ + 4e- 2H2

Ex. Electroplating – During electrolysis, a layer of a second metal can be deposited on the metal cathode.The purpose is to:

1/ improve the appearance of objects 2/ protect them from corrosion.

Silver baris a sourcefor platingthe spoon.

A steelspoon isthe objectto be plated.

At the silver bar, the neutral solid silver is oxidized: Ag(s) Ag+ + e-

The electrons are attracted to the positive side of the battery. The Ag+ ions enter solution and are attractedto the negative spoon.

Ex. Electroplating – During electrolysis, a layer of a second metal can be deposited on the metal cathode.The purpose is to:

1/ improve the appearance of objects 2/ protect them from corrosion.

Silver baris a sourcefor platingthe spoon.

A steelspoon isthe objectto be plated.

At the silver bar, the neutral solid silver is oxidized: Ag(s) Ag+ + e-

The electrons are attracted to the positive side of the battery. The Ag+ ions enter solution and are attractedto the negative spoon.

When they reach the steel spoon, the Ag+ ions gain electrons that come from the negative side of the battery and are reduced to solid silver:

Ag+ + e- Ag(s)This solid silver plates (covers) the steel spoon.

The battery holds the anode at a positivepotential and the cathode at a negative potential.

This is the opposite of a voltaic cell.

Ex. Electroplating – During electrolysis, a layer of a second metal can be deposited on the metal cathode.The purpose is to:

1/ improve the appearance of objects 2/ protect them from corrosion.

Silver baris a sourcefor platingthe spoon.

A steelspoon isthe objectto be plated.