The balanced chemical equation that describes the electrochemical cell that is represented by cell notation shown below is:

Fe(s)Fe3+(aq)I2(s)I–(aq)Pt(s)

Question

The balanced chemical equation that describes the electrochemical cell that is represented by cell notation shown below is:

Fe(s)Fe3+(aq)I2(s)I–(aq)Pt(s)

BlackTom AI · Accepted Answer

The problem provides a cell notation for an electrochemical cell and asks for the balanced equation describing the cell reaction.
Option 1: 'Fe(s) + I2(s) → Fe3+(aq) + 2I–(aq)'. This would imply iron metal is oxidized to Fe3+ in a single electron transfer and iodine is reduced to iodide with two electrons, which is not balanced for the electrons involved: Fe would need to lose three electrons to become Fe3+, not one, and I2 requires two electrons to form two I−. Thus this option misbalances both oxidation and reduction half-reactions.
Option 2: '2Fe3+(aq) + 2I–(aq) → 2Fe(s) + I2(s)'. Here iron(III) ions are reduced to Fe(s) and iodide is oxidized to I2, which is the reverse of the expected spontaneous cell flow for the given notation (Fe metal is on the left in the notation, indicating oxidation). The electron transfer direction is incorrect, and the oxidation state changes do not align with the cell notation.
Option 3: 'Fe3+(aq) + 2I–(aq) → Fe(s) + I2(s)'. This shows Fe3+ being reduced to Fe(s) and iodide being oxidized to I2, which would correspond to an improbable or non-spontaneous redox pair for the given electrode setup. It also has an electron accounting that does not balance properly for the overall reaction when Fe is on the left as solid and I2/I− on the right.
Option 4: '2Fe(s) +3I2(s) → 2Fe3+(aq) + 6I–(aq)'. This option correctly pairs the oxidation half-reaction Fe(s) → Fe3+(aq) + 3 e− (oxidation, as Fe is on the left in the notation) with the reduction half-reaction I2(s) + 2 e− → 2 I–(aq) (reduction, using  dvoj electrons per I2). Balancing electrons requires multiplying the iron oxidation by 2 (giving 6 e−) and the iodine reduction by 3 (consuming 6 e−), which yields the overall balanced equation shown here: 2 Fe + 3 I2 → 2 Fe3+ + 6 I−. This matches both the species present in the cell notation and the electron balance needed for a spontaneous cell reaction.
In summary, each option’s redox changes and electron balance were examined: Options 1–3 misalign oxidation states, electron bookkeeping, or the direction of electron flow relative to the given cell notation, while Option 4 correctly balances both mass and charge and aligns with the electrode arrangement Fe(s) | Fe3+(aq) || I2(s) | I−(aq) | Pt(s).

The balanced chemical equation that describes the electrochemical cell that is represented by cell notation shown below is: Fe(s)Fe3+(aq)I2(s)I–(aq)Pt(s)单项选择题

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