InterviewSolution
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InterviewSolution
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Which of the following represents the electrodes of the first kind ?A. `Zn^(2+)|Zn`B. `Fe^(3+), Fe^(2+)|Pt`C. `AgCl|Ag|Cl^(-)`D. `Pt|Cl_(2)|Cl^(-)` |
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Answer» Correct Answer - B It is a metal-insoluble salt-anion electrode. It consists of a metal `(Hg)` in contact with a saturated solution of its sparingly soluble salt `(HgCl_(2)`, calomel) and another solubel salt `(KCl)` having common anions `(Cl^(-))`. The saturated calomel electrode is often used as a reference electrode (secondary reference) in place of hydrogen elec-trode which is inconvenient and difficult to prepare. As a reference electrode, saturated calomel electrode is reversible and has a fixed potential. Mercurous chloride (calomel) is reduced to mearcury, when saturated calomel electrode `(SCE)` is used as cathode accord-ing to the equation: `Hg_(2)Cl_(2)+2e^(-)hArr 2Hg(1)+2Cl^(-)(aq.)` It can be represented as `Hg_(2)Cl_(2)|Hg|Cl^(-)`. The half-cell potential for saturated calomel electrode is `0.2682 V`. |
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