Which statement about pH meters is true?

Which statement about pH meters is true?

• A. They do not require calibration
• B. They measure only acidity
• C. They require regular calibration
• D. They must be used with distilled water always

Answer: (C)

Understanding pH meters means recognizing that they rely on a glass electrode to measure hydrogen ion activity, which tells you how acidic or basic a solution is. The key is that the electrode and electronics can drift over time due to aging, temperature, and sample conditions, so regular calibration with known buffer solutions is essential to keep readings accurate. Calibration aligns the instrument to standard pH values and often includes temperature compensation, which helps reflect the true pH of the sample. Because of drift and varying sample conditions, you can’t rely on a meter staying accurate without calibration. The other statements are not correct: a pH meter measures a range from acidic to basic, not just acidity; it does require calibration; and while you should rinse the electrode between samples, you don’t have to use distilled water for every measurement.

Understanding pH meters means recognizing that they rely on a glass electrode to measure hydrogen ion activity, which tells you how acidic or basic a solution is. The key is that the electrode and electronics can drift over time due to aging, temperature, and sample conditions, so regular calibration with known buffer solutions is essential to keep readings accurate. Calibration aligns the instrument to standard pH values and often includes temperature compensation, which helps reflect the true pH of the sample. Because of drift and varying sample conditions, you can’t rely on a meter staying accurate without calibration. The other statements are not correct: a pH meter measures a range from acidic to basic, not just acidity; it does require calibration; and while you should rinse the electrode between samples, you don’t have to use distilled water for every measurement.