GATE CE 2025 Set 2 — Question 49
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Environmental Engineering → Water Quality → Chemical Parameters
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Question
A compound has a general formula and molecular weight 187. A 935 mg/l solution of the compound is prepared in distilled deionized water. The Total Organic Carbon (TOC) is measured as 360 mg/l (as C). The Chemical Oxygen Demand (COD) and the Total Kjeldahl Nitrogen (TKN) are determined as 600 mg/l (as ) and 140 mg/l (as N), respectively (as per the chemical equation given below). Which of the following options is/are CORRECT?Atomic weight: C(12), H(1), O(16), N(14)
Correct answer
(A) a = 6; (B) b = 7; (C) c = 5
Solution
1.Molarity of the compound = .
2.TOC = . Moles of Carbon = . Since there are 'a' carbons per molecule, . (Option A is correct).
3.TKN = (as N). Moles of Nitrogen = . Since there are 'd' nitrogens per molecule, . (Option D is incorrect).
4.Molecular weight equation: . Substituting : .
5.COD = (as ). Moles of = . From the stoichiometry, moles of = . Substituting : .
6.Solving the system: and . Adding them: . (Option C is correct). Then . (Option B is correct).
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