In pH measurement, reference electrodes may include which of the following?

In pH measurement, reference electrodes may include which of the following?

• A. Silver-Silver Chloride
• B. Quinhydrone
• C. Hydroxide
• D. Hydrogen

Answer: (A)

Reference electrodes in pH measurement must provide a stable, well-defined potential that does not drift with the sample’s hydrogen ion activity. The silver-silver chloride reference electrode fits this role best because it uses a stable redox couple in contact with a saturated KCl solution, giving a reproducible potential across a wide pH range. This stability is what allows the glass pH sensor to produce consistent readings. Quinhydrone, while useful as a pH-sensing system in some setups, is not a true reference electrode; its potential changes with the sample and pH, so it cannot serve as the fixed reference. Hydrogen and hydroxide electrodes aren’t practical reference electrodes for routine pH meters because their potentials are more susceptible to drift and environmental conditions, making them unreliable as universal references.

Reference electrodes in pH measurement must provide a stable, well-defined potential that does not drift with the sample’s hydrogen ion activity. The silver-silver chloride reference electrode fits this role best because it uses a stable redox couple in contact with a saturated KCl solution, giving a reproducible potential across a wide pH range. This stability is what allows the glass pH sensor to produce consistent readings.

Quinhydrone, while useful as a pH-sensing system in some setups, is not a true reference electrode; its potential changes with the sample and pH, so it cannot serve as the fixed reference. Hydrogen and hydroxide electrodes aren’t practical reference electrodes for routine pH meters because their potentials are more susceptible to drift and environmental conditions, making them unreliable as universal references.