Question

Ferric chloride is effective over a pH range of __________

(a) 3.5-6

(b) 6.5-8

(c) 3.5-6.5

(d) 2-5

The question was asked in an online interview.

Enquiry is from Sedimentation with Coagulation in section Sedimentation of Environmental Engineering

Answer 1

The correct answer is (c) 3.5-6.5

For explanation I would say: Ferric chloride is effective over a pH range of 3.5-6.5 and above 8.5 whereas if Ferric sulfate is used then, it is effective over a pH range of 4-7 and above 9.