Water Quality Parameters MCQ with answer and solution

Concept

Carbonate and non-carbonate hardness

Formula

If TH > Alkalinity: carbonate hardness = alkalinity; non-carbonate hardness = TH − alkalinity

Step-by-step solution

1. Carbonate hardness is that part of hardness that is balanced by alkalinity (bicarbonates, carbonates). 2. When total hardness is greater than total alkalinity, carbonate hardness = total alkalinity. 3. Non-carbonate hardness = TH − alkalinity.

Explanation

Carbonate hardness cannot exceed the alkalinity, because alkalinity measures the carbonate and bicarbonate ions that pair with the hardness-causing cations. The excess hardness is non-carbonate.

Shortcut

TH > Alk → CH = Alk, NCH = TH − Alk. TH < Alk → CH = TH, NCH = 0.

Common mistake

Taking the difference as carbonate hardness.