Environmental Chemistry

Step 1: Understanding the Concept:
Chemical Oxygen Demand (COD) is a measure of the amount of oxygen required to chemically oxidize both organic and inorganic compounds in water. The test uses a strong chemical oxidant in an acidic medium.

Step 3: Detailed Explanation:
The standard method for COD analysis involves refluxing a water sample with a known excess of a strong oxidizing agent in a highly acidic solution.
$%5Cbegin%7Barray%7D%7Brl%7D%20%5Cbullet%20%26%20%5Ctext%7BOxidant%3A%20The%20most%20commonly%20used%20strong%20oxidant%20is%20potassium%20dichromate%20(K%20%5C(_2%5C)%20Cr%20%5C(_2%5C)%20O%20%5C(_7%5C)%20).%20Potassium%20permanganate%20(KMnO%20%5C(_4%5C)%20)%20can%20also%20be%20used%20but%20is%20less%20effective%20for%20many%20organic%20compounds.%7D%20%5C%5C%20%5Cbullet%20%26%20%5Ctext%7BAcid%3A%20The%20reaction%20is%20carried%20out%20in%20the%20presence%20of%20concentrated%20sulfuric%20acid%20(H%20%5C(_2%5C)%20SO%20%5C(_4%5C)%20).%20Sulfuric%20acid%20provides%20the%20necessary%20acidic%20environment%20and%20also%20helps%20to%20digest%20complex%20organic%20materials.%20Hydrochloric%20acid%20(HCl)%20is%20generally%20avoided%20because%20chloride%20ions%20can%20interfere%20with%20the%20oxidation%20reaction.%7D%20%5C%5C%20%5Cend%7Barray%7D$ Therefore, the standard combination of reagents for a COD assay is potassium dichromate and sulfuric acid.

Step 4: Final Answer:
The commonly used oxidants in COD assays are K $_2$ Cr $_2$ O $_7$ + H $_2$ SO $_4$ .

High-Yield Trend

Chapter Questions
1 MCQs

Official Solution

Environmental Chemistry

High-Yield Trend

Chapter Questions 1 MCQs

Official Solution

Chapter Questions
1 MCQs