One of the commonly used electrode is calomel electrode. Under which of the following categories, calomel electrode comes?

Solution

Chemistry ma’am · 2 steps

Write the calomel electrode in cell notation and count the three phases: metal, solid salt, anion.

1. What calomel is. Calomel is mercury(I) chloride, Hg₂Cl₂, a salt that barely dissolves in water. The electrode is liquid mercury coated with a paste of this salt and dipped in a KCl solution.

   Pt | Hg(l) | Hg₂Cl₂(s) | Cl⁻(aq) Hg₂Cl₂(s) + 2e⁻ → 2Hg(l) + 2Cl⁻(aq)

   Category	What is in it	Example
   Metal ion - metal	metal in a solution of its own ions	Zn²⁺ | Zn
   Oxidation - reduction	inert Pt in two ions of one element	Fe³⁺, Fe²⁺ | Pt
   Metal - insoluble salt - anion	metal, its sparingly soluble salt, and the salt's anion	Hg | Hg₂Cl₂ | Cl⁻, Ag | AgCl | Cl⁻
   Gas - ion	gas bubbled over Pt in a solution of its ions	Pt | H₂ | H⁺

2. So. The calomel electrode has a metal (Hg), its insoluble salt (Hg₂Cl₂) and the salt's anion (Cl⁻), so it is a metal - insoluble salt - anion electrode, option (c).

The idea to keep. To classify an electrode, list what is physically present. A metal, its sparingly soluble salt and that salt's anion make the calomel and silver-silver chloride family.

Answer from the NTA final answer key. Solution by PrepWiser.