Water chemistry fundamentals: Which statements about pH and its interpretation for acidity/alkalinity are correct for potable water assessment?

Introduction / Context:
pH is a master variable in water treatment, influencing corrosion control, coagulation efficiency, disinfection kinetics, and consumer acceptability. Understanding its scale and endpoints is foundational for process control.

Given Data / Assumptions:

• Standard pH scale from 0 to 14 at 25°C.
• Neutrality defined at pH 7 for pure water at 25°C.
• Extremes represent strong acidity or alkalinity.

Concept / Approach:

By definition, pH = −log10[H+]. Pure water at 25°C has [H+] = 10^-7 mol/L (pH 7). Lower pH values indicate increasing acidity; higher values indicate increasing alkalinity. Thus statements (a), (b), and (c) are simultaneously true.

Step-by-Step Solution:

Verification / Alternative check:

Any basic water-chemistry text lists pH endpoints and neutrality at 25°C; treatment setpoints often target pH 6.5–8.5 for distribution system stability.

Why Other Options Are Wrong:

• Option (e) excludes the valid statement (c).

Common Pitfalls:

• Forgetting temperature dependence of neutrality (slight shifts with temperature).

Final Answer:

All of the above.