CWS Water Chemistry & Contaminant Identification 3

Question 1

Which type of hardness cannot be removed by boiling water?

Accepted Answer

Permanent hardness

Answer

Permanent (non-carbonate) hardness is caused by calcium and magnesium sulfates and chlorides, which are not removed by boiling.

Question 2

Langelier Saturation Index (LSI) is used to predict water's tendency to:

Accepted Answer

Form or dissolve calcium carbonate scale

Answer

The LSI predicts whether water will precipitate (positive LSI) or dissolve (negative LSI) calcium carbonate scale.

Question 3

Arsenic contamination in groundwater is most commonly associated with:

Accepted Answer

Natural geological formations

Answer

Arsenic occurs naturally in many geological formations and can leach into groundwater, especially in anaerobic conditions.

Question 4

The presence of hydrogen sulfide gas in water is most commonly detected by:

Accepted Answer

Rotten egg odor

Answer

Hydrogen sulfide produces a distinctive rotten egg odor detectable at very low concentrations (below 0.5 ppb).

Question 5

Which ion is responsible for 'blue staining' on plumbing fixtures?

Accepted Answer

Copper (Cu²⁺)

Answer

Copper ions in water cause characteristic blue-green staining on sinks, tubs, and fixtures due to copper corrosion.

(CWS) Certified Water Specialist Practice Test