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:
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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