Which statement about pH is true?

• A. It measures the temperature of a solution
• B. It indicates how acidic or basic a solution is
• C. It shows the density of a solution
• D. It reflects the color of a solution

Answer: (B)

Understanding pH centers on how acidic or basic a solution is. pH measures the activity, or concentration, of hydrogen ions in the solution. A lower pH means more hydrogen ions and a more acidic solution; a higher pH means fewer hydrogen ions and a more basic (alkaline) solution, with 7 being neutral at standard conditions. The pH value is not a measure of temperature, density, or color. It’s also a logarithmic scale, so each unit change represents about a tenfold change in hydrogen ion concentration. For example, a solution with pH 3 is ten times more acidic than one with pH 4.