Water quality and hardness: Which statement best describes hard water in terms of lathering, potability, and environmental impact?

Introduction / Context:
Water hardness comes from multivalent cations (mainly Ca2+ and Mg2+). Understanding what hardness implies for domestic use, health, and the environment clarifies when treatment is required and when it is optional.

Given Data / Assumptions:

• “Hard water” refers to elevated calcium and/or magnesium levels.
• Soap lathering, scale formation, and potability are in focus.
• Environmental “pollution” implies harmful contamination beyond mere mineral content.

Concept / Approach:
Hardness reduces soap lather and forms scum and scale in heaters and pipes. However, hardness is not a toxic contaminant; most guidelines treat moderate hardness as acceptable or even beneficial for taste and mineral intake. Environmental pollution is not caused simply by hardness; pollution concerns relate to organic, toxic, or eutrophying substances.

Step-by-Step Solution:
Evaluate lather statement → false; hardness interferes with lather.Assess potability → generally safe; not inherently unfit for drinking.Assess pollution claim → hardness alone does not constitute pollution.Thus, the single correct statement is that hard water is not inherently unfit to drink.

Verification / Alternative check:
WHO/municipal standards recognize hardness as an aesthetic/operational parameter, not a primary health contaminant.

Why Other Options Are Wrong:

• “Does not affect lather” is wrong; Ca2+/Mg2+ form insoluble salts with soap.
• “Pollutes streams” is wrong; hardness minerals are naturally occurring.
• “All of the above” cannot be true because (a) and (c) are false.
• “Always unsafe” overstates the issue; hardness does not equal toxicity.

Common Pitfalls:
Equating nuisance scaling with health hazards; confusing hardness with contamination by heavy metals or pathogens.

Final Answer:
Hard water is not inherently unfit for drinking purposes