Applications of Redox

Electrochemistry

Review

• Oxidation reduction reactions involve a transfer of electrons.

• OIL-RIG • Oxidation Involves Loss• Reduction Involves Gain • LEO-GER • Lose Electrons Oxidation • Gain Electrons Reduction

• Solid lead(II) sulfide reacts with oxygen in the air at high temperatures to form lead (II) oxide and sulfur dioxide. Which substance is a reluctant (reducing agent) and which is an oxidant (oxidizing agent)?

• A. PbS, reductant; O2, oxidant

• B. PbS, reductant; SO2, oxidant • C. Pb2+, reductant; S2-, oxidant • D. PbS, reductant; no oxidant • E. PbS, oxidant; SO2, reductant

Balancing Redox Reactions by ½ Reactions –Acidic

• Potassium dichromate is a bright orange compound that can be reduced to a blue-violet solution of Cr3+ ions. Under certain conditions, potassium dichromate reacts with ethyl alcohol as follows:

• H+(aq) + Cr2O72- (aq) + C2H5OH (l) ↔Cr3+(aq) + CO2(g) + H2O(l)

• Balance this equation using the ½ reaction method.

Balancing Redox Reactions by ½ Reactions- (Basic) • Silver is sometimes found in nature as large nuggets; more often it is

found mixed with other meals and their ores. An aqueous solution containing cyanide ion is often used to extract the silver using the following reaction that occurs in basic solution.

• Ag(s) + CN-(aq) + O2(g) ↔ Ag(CN)2-(aq)

• Balance the equation using the ½ reaction method.

Applications

• Moving electrons is electric current • 8H+ + MnO4 + 5Fe2+ + 5e-

→ Mn+2 + 5Fe+3 + 4H2O