pH measures what?

• A. It measures the temperature of a solution.
• B. It measures the volume of solvent.
• C. It measures how acidic or basic an aqueous solution is.
• D. It measures the mass of solute.

Answer: (C)

pH measures how acidic or basic an aqueous solution is. It reflects the hydrogen ion activity (concentration) in the solution and is expressed on a log scale: low pH means high hydrogen ion concentration (acidic), high pH means low hydrogen ion concentration (basic). A neutral value is about 7 at standard room temperature; values below 7 indicate acidity, values above 7 indicate basicity. The concept is about the balance of hydrogen ions, not temperature, volume, or mass, so pH does not measure temperature, volume, or mass.