pH Meter | working of glass electrode of pH meter

Summary

This video provides an in-depth explanation of how pH meters work. It covers the two main components: the reference electrode and the glass electrode. The process of how pH is measured is explained through the interaction of hydrogen ions (H+) and the electrode surfaces, leading to changes in the electrical potential, which are then measured. The video also details how pH meters are calibrated using known buffer solutions to ensure accurate readings, making it a useful resource for understanding the science behind pH measurement and the workings of pH meters.

Takeaways

• 😀 The pH meter consists of two main electrodes: the reference electrode and the glass electrode.
• 😀 The reference electrode is filled with a saturated potassium chloride solution, while the glass electrode contains 0.1 M HCl.
• 😀 Both electrodes are made of silver wire coated with silver chloride, which plays a crucial role in the electrochemical reactions.
• 😀 The silver electrode undergoes reversible reactions where silver ions can either lose or gain electrons to form silver chloride or metallic silver.
• 😀 The glass electrode has a bulb made of thin glass designed to bind H⁺ ions, forming a hydrated gel layer on both sides of the glass.
• 😀 The hydrated gel layer is crucial for measuring pH as it allows H⁺ ions to bind on the inner and outer surfaces of the glass electrode.
• 😀 In acidic solutions, more H⁺ ions bind to the outer surface, creating a positive charge, while the inner side becomes less positive.
• 😀 In alkaline solutions, the H⁺ ions from the inner surface of the glass electrode are released into the solution, changing the electrode's potential.
• 😀 The potential difference generated by these reactions is measured with respect to the reference electrode to determine the pH.
• 😀 The pH meter needs to be calibrated using buffers with known pH values (e.g., pH 4, pH 7, and pH 10) to ensure accurate readings.
• 😀 Calibration involves measuring the potential difference across the electrodes in the buffer solutions and setting these values in the pH meter’s microchip.

Q & A

What are the two main components of a pH meter?

The two main components of a pH meter are the reference electrode and the glass electrode.

How is the reference electrode constructed?

The reference electrode is made of silver wire coated with silver chloride.

What is the reversible reaction that occurs in the reference electrode?

In the reference electrode, the silver metal can lose an electron to form silver ions, and the silver ions can also accept an electron to form metallic silver.

What role does the glass electrode play in the pH meter?

The glass electrode detects the concentration of hydrogen ions (H+) in the solution, which is essential for determining the pH of the solution.

What is the structure of the glass electrode?

The glass electrode has a bulb-like structure made of thin glass, which is composed of silica.

How does the glass electrode interact with H+ ions?

The glass is designed in such a way that its negatively charged oxygen atoms bind H+ ions from both the inner and outer sides, creating a hydrated gel layer.

What happens when the solution in contact with the glass electrode is acidic?

In an acidic solution, there are more H+ ions outside the glass electrode, making the outer layer more positive. The H+ ions bind to the inner layer, decreasing the concentration of free H+ ions inside the glass electrode.

What happens when the solution in contact with the glass electrode is alkaline?

In an alkaline solution, there are fewer H+ ions outside the glass electrode, making the outer layer less positive. The H+ ions inside the electrode are released to balance the charge, which causes a change in the potential of the electrode.

What is the function of the silver chloride in the reference electrode?

The silver chloride in the reference electrode reacts with chloride ions to form silver chloride, helping maintain the ion balance and allowing the reference electrode to maintain a constant potential.

Why is it important to calibrate the pH meter?

Calibrating the pH meter is crucial because it ensures accurate measurements by adjusting the device to register known pH values for the buffers used in calibration (pH 4, pH 7, and pH 10).