GATE CE 2025 Set 2 — Question 34
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Environmental Engineering → Drinking Water Treatment → Chlorination
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Question
Free residual chlorine concentration in water was measured to be (as ). The of water is . By using the chemical equation given below, the concentration (in ) in water is ________________ (round off to one decimal place).Atomic weight:
Correct answer
2.5 to 2.6
Solution
1.Calculate the total molar concentration of free residual chlorine (FRC):
The FRC is given as as .Molecular weight of .
Total concentration .
2.Use the equilibrium equation for HOCl dissociation:
The equilibrium constant is given by:3.Determine the concentration of from pH:
4.Find the ratio of to :
Thus, .5.Calculate :
Total FRC concentration .6.Final Answer:
Rounding to one decimal place, the concentration of is . The provided answer range is to .Continue learning with Success Tracker
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