Question

At what pH, chlorine exists as molecular chlorine?

(a) 3

(b) 5

(c) <5

(d) <10

I had been asked this question during a job interview.

I'd like to ask this question from Chlorination in chapter Properties of Disinfection of Environmental Engineering

Answer 1

Correct option is (c) <5

To elaborate: When chlorine is added to water, the chlorine acts as molecular chlorine only when its pH is less than 5.