Electrochemistry

• Understand Redox reactions involve a transfer of electrons.

• Develop a metals activity series experimentally.

• Predict spontaneous reactions using an activity series.

Burning and corrosion needs oxygen – oxidation.

Oxidation-reduction reactions – (redox)Chemical changes when electrons are transferred

from one reactant to another.

Oxidation - an atom loses one or more electrons.Reduction - an atom gains one or more electrons.

"LEO says GER” Losing Electrons is Oxidation, Gaining Electrons is Reduction

Atoms fight for electrons.

The strongest takes electrons from other substance.

Strongest is reduced (gains), weakest is oxidized (loses).

Metals do not gain electrons and are always oxidized.

2 Ag+(aq) + Cu(s) ??

2 Mg (s) + O2 (g) → 2 MgO (s)

Mg – neutralMg2+ ion

O – neutral O2– ion

Magnesium is . Oxygen is reduced.Mg → Mg2+ + 2e- O + 2e- → O2-

These are called “half-reactions.”

Half-reactions show the oxidation or reduction reaction separated.

Cu(s) + 2 AgNO3(aq) → Cu(NO3)2(aq) + 2 Ag(s)

Oxidation: Cu → Cu2+ + 2e–

Reduction: Ag+ + 1e– → Ag

Half reactions are often shown as aqueous net ionic equations – spectator IONS not included.

+2+10 0

2 Ag+(aq) + Cu(s) →

Ag(s) + Cu2+(aq) →

Ag+ ions can oxidize Cu metal.Cu2+ cannot oxidize Ag metal.

Cu metal can reduce Ag+ ions.Ag metal cannot reduce Cu2+ ions.

2 Ag(s) + Cu2+(aq)

no reaction

Spontaneous rxns occurs without added energy.

Metal Activity Series Lab