Basic water chemistry: Water having pH = 6 at ambient conditions is classified as

Difficulty: Easy

Correct Answer: acidic

Explanation:

Introduction / Context:The pH scale quantifies acidity/alkalinity of water on a logarithmic basis. Understanding pH classifications is essential for corrosion control, coagulation, disinfection efficacy, and consumer acceptability in water-supply engineering.

Given Data / Assumptions:

  • Neutral pH at 25°C is approximately 7.0.
  • Values below 7 are acidic; values above 7 are alkaline (basic).
  • Measured pH is 6.

Concept / Approach:Classify pH numerically relative to neutrality. Consider implications for pipe materials and treatment chemistry (e.g., alkalinity adjustment, corrosion indices).

Step-by-Step Solution:

Compare measured pH (6) with neutral value (7).Since 6 < 7, the water is acidic.Acidic water may require pH adjustment/alkalinity addition to reduce corrosion potential.

Verification / Alternative check:Logarithmic nature: each pH unit represents a tenfold change in hydrogen-ion activity, so pH 6 is ten times more acidic than pH 7 (in terms of [H+]).

Why Other Options Are Wrong:Alkaline and neutral categories contradict the numeric definition; “none of these” is unnecessary because “acidic” is exact.

Common Pitfalls:Ignoring temperature effects on neutral pH (slight shift from 7.0), which does not change classification here.

Final Answer:acidic

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