Question

Calomel electrode is made up of _______

• A. \( \text{Pool of mercury} \)
• B. \( \text{Hg/Hg}_2\text{Cl}_2 \)
• C. \( \text{Ag/AgCl}_2 \)
• D. \( \text{Pt/KCl} \)

Hint:

Remember "calomel" (Hg$_2$Cl$_2$) is the key component along with mercury (Hg) in a calomel electrode.

Answer 1

The Correct Option is B

The calomel electrode is a type of reference electrode commonly used in electrochemical measurements. It consists of liquid mercury in contact with a paste of mercury(I) chloride (Hg$_2$Cl$_2$), also known as calomel, and a solution containing chloride ions (typically potassium chloride, KCl) at a specific concentration. The notation Hg/Hg$_2$Cl$_2$ represents this composition. The potential of the calomel electrode is stable and depends on the concentration of the chloride solution. Option A describes just mercury, which is a component but not the entire electrode system. Option C describes a silver/silver chloride reference electrode. Option D describes a platinum electrode in a potassium chloride solution, which is not a calomel electrode.