In a cell of normal hydrogen electrode and calomel electrode, the electrode reaction taking place at calomel electrode will be

Options

A. `Hg_2CI_(2(s))to2Hg_((I))+2CI^(-)+2e^(-)`
B. `2Hg_((I))+2CI^(-)toHg_2CI_(2(s))+2e^(-)`
C. `Hg_2CI_(2(s))+2e^(-)to2Hg_((I))+2CI^(-)`
D. none of these.

Answer

C

Explanation

A calomel electrode consists of mercury at the
bottom over which a paste of mercury-mercurous chloride is
placed. A solution of potassium chloride is then placed over
the paste. A platinum wire sealed in a glass tube helps in
making the electrical contact. The electrode is connected with
the help of the side tube, on the left through the salt bridge with
the other electrode to make complete cell. When a calomel
electrode is used with a normal hydrogen electrode then the
electrode reaction taking place when the electrode acts as
cathode is
`1/2Hg_2CI_2+e^(-)hArrHg+CI^(-)`
`Hg_2CI_(2(s))+2e^(-)hArr2Hg_((I))+2CI^(-)`