Electrochemistry: Electrode Potential and Reference Electrodes

pH Meter

• The electrode potential is constant due to the constant chloride ion concentration (0.1 M).

Reference Electrode (Calomel Electrode)

• It is used to complete the electrical circuit.
• A common reference electrode is another Ag/AgCl electrode.
• The Ag/AgCl electrode is immersed in a 0.1 M KCl solution, making contact with the test solution through a porous fiber.

Components of pH Meter

• Electrode holder
• Amplifier: amplifies the electrical charge from the electrode and passes it to the galvanometer as readable current.
• Galvanometer or Digital display
• Temperature knob: controls the temperature.
• Adjustment knob: adjusts the pH meter before taking readings.

Advantages of pH Meter

• pH calibration is low-priced and robust.
• Pocket size pH meters are user-friendly.
• Accounts are reliable and specific.
• Readings are accurate and precise.

Disadvantages of pH Meter

• Heat affects the output readings.
• pH calibration using glass electrodes requires cleaning to prevent deposition influencing the readings.

Application of pH Meter

• In agriculture industries, it measures the pH of soil.
• In municipal water supplies, it measures water quality.
• In chemical and pharmaceutical industries, it measures the pH value of solutions.
• In the food industry, it is used for dairy products like cheese, curds, and yogurts.

Maintenance of pH Meter

• Cleaning lines of the probes is essential for accuracy and precision.
• Probes are kept moist when not in use with a medium.
• Electrodes should not be allowed to become dry.
• Regular calibration of pH meter is essential.

pH Scale

• pH is a symbol that describes the degree of acidity or alkalinity.
• It is measured on a scale of 0 to 14.
• pH is derived from the negative logarithm (P) and the chemical symbol for Hydrogen (H).

pH Value

• It is directly related to the ratio of hydrogen ion (H+) and hydroxyl ion (OH-) concentrations.
• If H+ concentration is higher than OH- concentration, the material is acidic (pH < 7).
• If OH- concentration is higher than H+ concentration, the material is basic (pH > 7).
• If H+ concentration is equal to OH- concentration, the material is neutral (pH = 7).

Types of pH Meter

• Portable pH meter: covers an extensive range of regularly employed instruments.
• Desktop pH meter: ideal for laboratory use.
• Pen pH meter: composed of a single scale, conventional measurement range for easy and handy equipment.

Electrode

• There are two types of electrodes: glass electrode (measuring electrode) and Ag/AgCl electrode.
• The Ag/AgCl electrode carries current through the half-cell reaction.