JEE Main 2023 — Environmental Chemistry Question with Solution
From: JEE Main 2023 (Online) 11th April Morning Shift
Question
Given below are two statements:
Statement I : If BOD is 4 ppm and dissolved oxygen is 8 ppm, then it is a good quality water.
Statement II : If the concentration of zinc and nitrate salts are each, then it can be a good quality water.
In the light of the above statements, choose the most appropriate answer from the options given below :
Choose an option
Show full solutionCorrect option: C
Step-by-step explanation
Statement I : If BOD is 4 ppm and dissolved oxygen is 8 ppm, then it is a good quality water.
Statement II : If the concentration of zinc and nitrate salts are 5 ppm each, then it can be a good quality water.
The Biochemical Oxygen Demand (BOD) measures the quantity of oxygen used by microorganisms in the oxidation of organic matter. Lower values of BOD indicate better water quality. A BOD value of less than 5 ppm indicates good quality water. Therefore, in Statement I, the BOD value of 4 ppm indicates good water quality.
Dissolved oxygen (DO) refers to the level of free, non-compound oxygen present in water. DO levels above 5-6 ppm are generally good for aquatic life. In Statement I, the DO level of 8 ppm suggests the water is of good quality.
The concentration of zinc in clean water should not exceed 5 ppm and the concentration of nitrates should not exceed 50 ppm. In Statement II, both zinc and nitrate concentrations are given as 5 ppm, which are within their respective permissible limits, therefore suggesting the water can be of good quality.
Hence, based on this analysis :
Option C : Both the statements I and II are correct.
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