Which statement about pH meters is true?

Which statement about pH meters is true?

• A. To measure the pH of a solution
• B. To calibrate with buffers
• C. To adjust the pH by adding acid or base
• D. To monitor dissolved oxygen levels

Answer: (A)

A pH meter is designed to measure the hydrogen ion activity in a solution, giving you its pH value. The glass electrode responds to the concentration of H+, and the meter converts that response into a pH reading. That direct measuring action is why the statement about measuring the pH of a solution is true—the meter’s primary purpose is to report pH. Calibration with buffer solutions is a necessary preparation step to ensure accuracy, since known-buffer readings set the instrument's baseline. But calibrating with buffers is something you do to prepare the meter for accurate measurements, not the ongoing function of reading pH itself. The other activities—adjusting the pH by adding acid or base, or monitoring dissolved oxygen—are separate actions or measurements, not what the pH meter does.

A pH meter is designed to measure the hydrogen ion activity in a solution, giving you its pH value. The glass electrode responds to the concentration of H+, and the meter converts that response into a pH reading. That direct measuring action is why the statement about measuring the pH of a solution is true—the meter’s primary purpose is to report pH.

Calibration with buffer solutions is a necessary preparation step to ensure accuracy, since known-buffer readings set the instrument's baseline. But calibrating with buffers is something you do to prepare the meter for accurate measurements, not the ongoing function of reading pH itself. The other activities—adjusting the pH by adding acid or base, or monitoring dissolved oxygen—are separate actions or measurements, not what the pH meter does.