Question:
In COD method the oxidant used is a mixture of -
In COD method the oxidant used is a mixture of -
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To prevent interference from chloride ions (\(\text{Cl}^-\)) present in wastewater (which can also be oxidized by dichromate, giving false high COD readings), mercuric sulfate (\(\text{HgSO}_4\)) is added to complex and mask the chlorides.
Updated On: Aug 20, 2026
- Potassium dichromate and concentrated sulphuric acid
- Potassium dichromate and concentrated nitric acid
- Potassium permanganate and concentrated sulphuric acid
- Potassium permanganate and concentrated nitric acid
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Chemical Oxygen Demand (COD) is an essential water quality parameter that measures the total organic matter in wastewater susceptible to chemical oxidation.
Step 2: Detailed Explanation:
The standard COD wet-digestion method utilizes a highly powerful chemical oxidant mixture:
- Potassium dichromate (\(\text{K}_2\text{Cr}_2\text{O}_7\)): Serves as the primary oxidizing agent.
- Concentrated sulfuric acid (\(\text{H}_2\text{SO}_4\)): Serves as the acid medium to ensure maximum oxidation potential. It also contains silver sulfate (\(\text{Ag}_2\text{SO}_4\)) as a catalyst to accelerate the oxidation of straight-chain hydrocarbons.
The mixture is refluxed at high temperatures, converting all organic carbon into carbon dioxide and water.
Step 3: Final Answer:
The oxidant mixture consists of Potassium dichromate and concentrated sulphuric acid, which corresponds to option (A).
Chemical Oxygen Demand (COD) is an essential water quality parameter that measures the total organic matter in wastewater susceptible to chemical oxidation.
Step 2: Detailed Explanation:
The standard COD wet-digestion method utilizes a highly powerful chemical oxidant mixture:
- Potassium dichromate (\(\text{K}_2\text{Cr}_2\text{O}_7\)): Serves as the primary oxidizing agent.
- Concentrated sulfuric acid (\(\text{H}_2\text{SO}_4\)): Serves as the acid medium to ensure maximum oxidation potential. It also contains silver sulfate (\(\text{Ag}_2\text{SO}_4\)) as a catalyst to accelerate the oxidation of straight-chain hydrocarbons.
The mixture is refluxed at high temperatures, converting all organic carbon into carbon dioxide and water.
Step 3: Final Answer:
The oxidant mixture consists of Potassium dichromate and concentrated sulphuric acid, which corresponds to option (A).
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