Which of the following pH levels indicates a neutral substance?

• A. 0
• B. 7
• C. 14
• D. 6.5

Answer: (B)

A pH level of 7 indicates a neutral substance because it is the point at which the concentration of hydrogen ions (H+) is equal to the concentration of hydroxide ions (OH-) in a solution. This balance occurs in pure water, which is the standard reference for pH.

In the pH scale, values below 7 represent acidic conditions, where hydrogen ion concentration is higher than that of hydroxide ions, while values above 7 represent basic (or alkaline) conditions, where hydroxide ion concentration exceeds that of hydrogen ions. This understanding of the pH scale is fundamental in various scientific applications, especially in chemistry and environmental science, where determining acidity or alkalinity is crucial for reactions and environmental assessments.