CHAPTER 8- OXIDATION-REDUCTION REACTIONS (REDOX) Flashcards
• involve a change in valence of reacting substances
• goes side-by-side, thus named as Redox
Oxidation-Reduction
• Oxidation is gain of oxygen.
• Reduction is loss of oxygen.
Redox in Terms of Oxygen
Transfer
• These are old definitions which aren’t used very much nowadays. The most likely
place you will come across them is in organic chemistry.
– Oxidation is loss of hydrogen.
– Reduction is gain of hydrogen.
Oxidation in Terms of Hydrogen Transfer
• Oxidation is loss of electrons.
• Reduction is gain of electrons.
• OIL-RIG
Redox in Terms of Electron
Transfer
• substance that cause an
increase in oxidation
number
• used in the analysis of
reducing agents
Oxidising Agent
- Potassium Permanganate
- Potassium Dichromate
- Potassium Bromate
- Potassium Iodate
- Potassium Ferricyanide
- Ceric Sulfate
- Ferric Ammonium Sulfate (FAS)
- Iodine
- Bromine
Common Oxidizing Agents
The substance that cause a decrease in oxidation number
Reducing Agent
- Ferrous Ammonium Sulfate
- Sodium Thiosulfate
- Oxalic Acid
- Potassium Arsenite
- Titanium Chloride
- Ascorbic Acid
Common Reducing Agents
Ex: Assay of Hydrogen Peroxide
- sample is titrated directly with KMnO4
Direct Titration
*Titration in which an excess standard KMnO4 solution is employed to oxidize a substance and the amount in excess is determined by reduction with:
- excess standard oxalic acid
- excess ferrous ammonium sulfate and back titration with more standard KMnO4
* Titration in which an excess standard of oxalic acid solution is added to the substance and the excess oxalic acid is titrated with standard KMnO4
(Ex: Assay of Sodium Nitrate)
Residual Titration
- Reaction is in acidic solution
- Standard permanganate is the titrant in direct and indirect method
- No indicator is required
Permanganometry
- Ceric Sulfate - stronger oxidizing agent than KMnO4
- Ferrous phenanthroline (ferroin) is the indicator
- For complex sample which is red in color
Cerimetry
