Which transformation could take place at the anode of an electrochemical cell? Which transformation could take place at the anode of an electrochemical cell? O2 to H2O Cr2O72- → Cr2+ F2 toF− HAsO2 to As None of the above could take place at the anode.

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Answer:

None of the above could take place at the anode.

Explanation:

In a cell, a redox reaction takes place, so one substance must reduce (gain electrons), and others must oxidize (lose electrons). At the anode, the substance oxidizes, and at the cathode the substance reduces.

Thus, we need to find what transformation oxidation is happening. To this, let's calculate the oxidation number (nox) of the atoms. If it's increasing, and oxidation is happening, if it's decreasing, a reduction is happening.

O₂ to H₂O:

O2 is a simple substance, so it has nox = 0. In a compound, O has nox -2 and H +1, so the nox of O is decreasing.

Cr₂O₇⁻² → Cr⁺²:

O has nox -2, so let's call the nox of Cr as x:

2x +7*(-2) = -2

2x -14 = -2

x = +6

And Cr⁺² has nox +2, so it's reducing.

F₂ to F⁻:

F₂ is a simple substance, so F has nox 0, and F⁻ has nox -1, then it's reducing.

HAsO₂ to As:

H has nox +1, and O has nox -2, so calling x the nox of As:

+1 + x + 2*(-2) = 0

1 + x - 4 = 0

x = +3

And As is a simple substance, that has nox 0, the it's reducing.

Thus, none of them is oxidizing, and none of them could take place at the anode.

None of the transformations could take place at the anode of an electrochemical cell.

What reactions occur at the anode?

At the anode of an electrolytic or electrochemical cell, oxidation reactions occur.

Oxidation reactions are reactions in which electron loss or increase in oxidation number of species occur.

From the given reaction:

  • O₂ to H₂O is a reduction reaction in which oxidation number of O goes from 0 to -2
  • Cr₂O₇²⁻ → Cr2+ is a reduction reaction in which the oxidation number of Cr goes from +6 to +3
  • F₂ to F⁻ is a reduction reaction in which the oxidation number of F goes from 0 to -1

Therefore, none of the transformations could take place at the anode of an electrochemical cell.

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