Understanding Voltaic Cells: The Role of Fe3+ in the Anode

[Precursor]

The problem I have is just a detail I want to clarify about the voltaic cell.

A standard cell is a voltaic cell in which each half-cell contains all entities shown in the half-reaction equation at SATP conditions, with a concentration of 1.0 mol/L for the aqueous solution.

Referring to the both the definition and the diagram, what I'm wondering is: why is it necessary to have the Fe 3+ (aq) in the anode solution? It's the product of the oxidation reaction occurring there, so why is it neededthere initially ? This includes not only the particular cell shown above, but all voltaic cells. In general, why is it necessary to have the product of the half-reaction in the anode half? What function does it serve in the cell?

 

[Borek]

Generally speaking - there is no need for products to be present initially. They will appear immediately given chance

However, at STP - by definition - activity of every reagent involved is 1.

 

[Blueshift5]

I can provide some clarification on the role of Fe3+ in the anode of a voltaic cell. First, it is important to understand that voltaic cells operate based on redox reactions, where one species is oxidized (loses electrons) and another is reduced (gains electrons). In the case of the anode, the species being oxidized is Fe2+ (aq), which is converted into Fe3+ (aq).

The presence of Fe3+ (aq) in the anode solution is necessary for two reasons. Firstly, it serves as the oxidizing agent in the anode half-reaction. Without Fe3+ (aq), the oxidation of Fe2+ (aq) cannot occur, and therefore the cell cannot generate an electrical current.

Secondly, Fe3+ (aq) also plays a crucial role in maintaining the electrical neutrality of the cell. As electrons are transferred from the anode to the cathode through an external circuit, there is a buildup of negative charge in the anode solution. The presence of Fe3+ (aq) allows for the balancing of this negative charge through the formation of Fe2+ ions, ensuring that the cell remains electrically neutral.

In summary, Fe3+ (aq) is necessary in the anode of a voltaic cell as it serves as the oxidizing agent and helps maintain the electrical neutrality of the cell. Without its presence, the cell cannot function properly and generate an electrical current. I hope this helps clarify the role of Fe3+ in the anode of a voltaic cell.