Question

C.O.D stands for
(a)Chemical oxygen demand
(b)Control of diesel
(c)Cesium Oxide deposition
(d)Chemistry of deposition

Answer 1

Hint: The laboratory test to determine organic matter present in the given wastewater. More the amount of organic matter present in the water, requires more oxygen to oxidise which makes water non-potable.

Complete answer:
The total amount of oxygen required to chemically oxidize the biodegradable and non- biodegradable organic matter is termed as chemical oxygen demand of the water. It is expressed in milligrams per liter or ppm which indicates the mass of oxygen consumed per liter of solution.

Additional Information: - The amount of oxygen required to oxidize organic matter completely present into carbon dioxide and water and other oxidized species.
-The given water sample is refluxed in a strongly acidic solution with a known excess amount of potassium dichromate.
-After the digestion, the remaining unreduced potassium dichromate is titrated with ferrous ammonium sulfate to determine the amount of potassium dichromate consumed.
-COD results are available much sooner than the BOD test result and require fewer manipulations of the sample.

So, the correct answer is ‘Chemical oxygen demand.’

Note: -Earlier times potassium permanganate was used as an oxidizing agent but soon replaced by other agents as being not able to oxidize very effectively all the organic matter.
-Nowadays oxidizing agents like ceric sulfate, potassium iodate, and potassium dichromate are also used.
-Potassium dichromate is most effective as it is able to oxidize all organic matter, relatively cheap, and easy to purify.