1. VII.Corrosion of Metals  Any metal corroding is simply that metal being oxidized.  The result is often the formation of metallic oxides. eg: CuO  Turquoise color of the roof of the Hotel Vancouver and Statue of Liberty) eg: Formation of rust Fe  Fe 2+ + 2e - H 2 O + ½O 2 + 2e -  2OH - Fe + H 2 O + ½O 2  Fe(OH) 2 Fe(OH) 2 + H 2 O + ½O 2  Fe(OH) 3 Fe(OH) 3  Fe 2 O 3 + 3H 2 O “Rust” is both Fe 2 O 3 and Fe(OH) 3 Step 1 Step 2 Step 3 Sun

2. Note: Never store different metals in contact with each other… One metal will speed up corrosion of the other. eg: H2OH2O Fe  Fe 2+ + 2e - Cu 2+ + 2e -  Cu CuO + H 2 O  Cu(OH) 2  The presence of the Cu speeds up the oxidation of the iron (a simple electrochemical cell has been created) then… Fe Cu  This technique could be used to protect the Cu from oxidizing if you don’t care about losing Fe. (Cathodic protection)

3. Preventing Corrosion:  Paint surface.  Galvanize: use a thin layer of zinc to protect underlying metal. eg: galvanized nails are iron or steel nails dipped in molten zinc.  Cathodic protection: one metal is sacrificed to protect another. eg: strips of zinc are used to protect iron hulls of ships. The zinc is more easily oxidized than the iron. (As zinc strips breakdown they are replaced)

4. VIII.Redox Titrations  One substance is used to determine concentration of another. eg: MnO 4 - + 8H + + 5Fe 2+  Mn 2+ + 4H 2 O + 5Fe 3+ PurpleColourless If 27.4mL of 0.020M KMnO 4 is used to titrate 25.0mL of a solution of Fe 2+, what is the concentration of Fe 2+ ? Moles of MnO 4 - : 0.0274L0.020mol L = 5.5x10 -4 mol Moles of Fe 2+ : 5.5x10 -4 mol MnO 4 - 5 mol Fe 2+ 1 mol MnO 4 - = 2.7x10 -3 mol [ Fe 2+ ] = 2.7x10 -3 mol 0.025L = 0.11M

5. IX.Breathalyser Function  Redox reaction is used. OrangeGreen CH 3 CH 2 OH + Cr 2 O 7 2- + 8H +  CH 3 CH + 2Cr 3+ + H 2 O O  Alcohol (CH 3 CH 2 OH) from breath reacts with Cr 2 O 7 2-  The more alcohol that is present, the more Cr 3+ is produced and reaction goes from orange to green. (monitored by computer)