Question

One degree of hardness is equivalent to ___ ppm.

(a) 2

(b) 1

(c) 10

(d) 100

I have been asked this question in an international level competition.

My enquiry is from Chemical Characteristic of Water in division Quality of Water of Environmental Engineering

Answer 1

Correct choice is (b) 1

For explanation I would say: Water is said to have one degree of hardness when its soap destroying power is equivalent to the effect of 14.25mg of calcium carbonate in one litre of water.