Asked in UHS MDCAT 2017 2017Moderate

The E0 value of the standard copper half cell is 0.34, measured when it is connected withthe SHE i.e. Standard Hydrogen Electrode. In this case the half cell reaction taking place atSHE is:

Correct answer: B. H2(g) → 2H+(aq) + 2e-

  • A. 2H+(aq) + 2e- → H2(g)
  • B. H2(g) → 2H+(aq) + 2e-
  • C. 2H+(aq) + 2e- → 2H(g)
  • D. 2H2- → 2H(g) + 2e-

Explanation

The Standard Hydrogen Electrode (SHE) serves as a benchmark for measuring standard electrode potentials, with a potential of 0 V. In the given context, the copper electrode is positive, making the SHE the anode. Thus, oxidation occurs at the SHE, involving the conversion of hydrogen gas (H2) into hydrogen ions (2H+) and electrons (2e-), as represented by the correct option B. Option A represents reduction, not oxidation. Option C describes an atom formation not typical at the SHE. Option D depicts an erroneous reaction involving a non-existent species.

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About Standard Hydrogen Electrode

The standard hydrogen electrode provides the reference potential of 0.00 V for measuring electrode potentials. It consists of platinum in contact with hydrogen gas at standard pressure and hydrogen ions at standard concentration, usually at 25°C, and can operate as either the oxidation or reduction half-cell.

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