Explain construction and working of glass electrode.

2.B] Explain construction and working of glass electrode.

Answer:

construction and working of glass electrode:

Glass electrode is pH sensitive electrode which can selectively detect and measures H⁺ ions in a system. Thus, it is widely used for pH measurements.

Glass electrode consists of a long glass tube with a thin-walled glass bulb at one end as shown in figure. The bulb contains 0.1M HCl. Ag/AgCl electrode (internal reference electrode) is placed in the solution and connected by a platinum wire for external contact.

The electrode is represented as,

Ag│ AgCl │ 0.1 M HCl │ Glass membrane

Working:

When the glass electrode is dipped in the test solution (xM), the Na_⁺ ions of the glass membrane are exchanged for H⁺ ions of the solution inside & outside. The reaction is ion-exchange.

The boundary potential E_b is established due to the above reaction. The glass electrode potential E_G is given by.