Question

The function of the reference electrode in a pH meter is to provide

• A. A constant current
• B. A constant voltage
• C. Temperature compensation
• D. A constant power

Hint:

Think of the reference electrode as the "sea level" on a map. You can only measure the height of a mountain (the pH) if you have a stable, constant starting point to measure from.

Answer 1

The Correct Option is B

A pH meter is essentially a high-impedance voltmeter that measures the potential difference between two electrodes submerged in a solution. To accurately measure the variable potential created by the hydrogen ion concentration, a stable baseline is required. 1. The Measuring System: The system consists of a glass (measuring) electrode and a reference electrode. The glass electrode develops a potential that changes according to the pH of the solution being tested.

2. The Role of the Reference Electrode: For the voltmeter to provide a meaningful reading, it must compare the variable potential of the glass electrode against a known, stable, and unchanging value. The reference electrode is designed to maintain a constant voltage (potential) regardless of the pH or the chemical composition of the test solution.

3. Maintaining Stability: Standard reference electrodes, such as the Saturated Calomel Electrode (SCE) or the Silver/Silver Chloride (Ag/AgCl) electrode, use a stable internal chemical environment to ensure that the baseline potential remains fixed. Without this constant voltage reference, it would be impossible to determine which portion of the measured potential change is actually due to pH variations.