Question

The pH scale is a logarithmic scale ranging from 0−14. A pH of 7 is considered neutral and represents

a) an equal number of H⁺ and OH⁻ in solution.
b) pure water.
c) an equal number of protein and lipid molecules in solution.
d) an excess of H₂O molecules compared to protein or lipid molecules.
e) an equal number of Na⁺ and Cl⁻ molecules in solution.

Answer 1

A pH of 7 on the pH scale represents an equal number of H⁺ and OH⁻ ions in solution, indicating a neutral environment, typically found in pure water but not exclusive to it.

Step-by-step explanation:

The pH scale is a logarithmic scale that indicates the acidity or basicity of an aqueous solution. Measured on a scale from 0 to 14, with 7 being neutral, it represents the negative logarithm of the hydrogen ion (H+) concentration in a solution. The correct answer to the question is: a pH of 7 is considered neutral and represents (a) an equal number of H⁺ and OH⁻ in solution.

A solution with a pH of 7 has a hydrogen ion concentration of 1.0 × 10⁻⁷ M, which is the same as the hydroxide ion concentration in pure water, rendering the solution neutral. This neutrality signifies neither an acidic nor a basic environment but rather one that is balanced. The pH of 7 aligns with the neutral point of pure water, although it does not necessarily imply the solution is pure water itself. It means that there is no net acidity or alkalinity present. Misconceptions such as pH representing protein/lipid balance or Na⁺/Cl⁻ concentrations are incorrect, as pH specifically pertains to H⁺ and OH⁻ levels.