A pH meter measures the acidity or basicity of a solution by determining the voltage difference between a glass electrode and a reference electrode. This voltage difference is directly related to the hydrogen ion concentration (H+) in the solution, which is the foundation of the pH scale. The Nernst equation describes the relationship between electrode potential and hydrogen ion concentration.
Elaboration:
1. pH Scale:
The pH scale ranges from 0 to 14, with 7 being neutral. Values below 7 indicate acidity, and values above 7 indicate basicity (alkalinity).
2. Electrodes:
A pH meter utilizes a glass electrode, which is sensitive to the hydrogen ion concentration, and a reference electrode with a known, stable potential.
3. Voltage Measurement:
When the electrodes are immersed in a solution, a voltage difference develops between them, which is directly proportional to the H+ concentration.
4. Nernst Equation:
The Nernst equation mathematically describes the relationship between the electrode potential, temperature, and hydrogen ion concentration.
5. Calculation:
The pH meter measures this voltage difference and, using the Nernst equation, calculates the pH value, which represents the negative logarithm of the H+ concentration.
6. Calibration:
Before use, the pH meter is calibrated with buffer solutions of known pH values to ensure accurate measurements.
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