# Is the ionic solution of a half-cell part of the electrode in a electrochemical cell? [closed]

A simple electrochemical cell consists of two half-cells, that is: a metal solid submerged in a solution. Additionally, there is salt bridge connecting the half-cells.

Ex: $\ce{Cu(s)}$ in $\ce{CuSO4(aq)}$ and $\ce{Zn(s)}$ in $\ce{ZnSO4(aq)}$

According to my text-book (Chemistry: Collins 3rd Edition, pg.506), the 'electrode' in a electrochemical cell is the whole half-cell.

"In work on electrochemical cells, however, the term electrode is extended to include what is known as a half-cell. So it refers not only to the conductor, but also to the conducting solution in which it is placed."

From other sources, I get the idea that the electrode is the metal solid (ex. $\ce{Zn}$), while the $\ce{ZnSO4}$ is an electrolyte (a solvent that seperates the cations and anions). Even when they are talking in the context of an electrochemical cell.

However, would not the saltbridge be considered the electrolyte as that is the compound that actually neutralizes the half-cells, through a seperation of cations and anions that travel to respective half-cells. While the redox reactions is actually happening between the $\ce{Zn(s)}$ and the $\ce{Cu^2+(aq)}$, which includes the metal solid and the ionic solution. As they are both conducting electrons.

Or are both the ionic solution and the saltbridge made of an electrolyte. Both consists of polar solvents, that seperate cations and anions. Therefore the electrode would be a metal solid in an electrolyte.

I guess the essence of my question, comes to down how to define electrode and electrolyte in the context of an electrochemical cell.

## closed as unclear what you're asking by Mithoron, airhuff, aventurin, Todd Minehardt, pH13 - Yet another PhilippMay 27 '18 at 22:27

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• I think you should clarify this a bit. It seems to me this is about cases like glass electrode where you have it kinda "all in one". – Mithoron May 23 '18 at 20:45

I haven't read the Collins book, but, in general, the electrode is the metallic conductor that connects a circuit to the "non-metallic" part of the circuit. The electrolyte is this non-metallic part - dissociated ions that conduct electricity. Note electrolyte has broader uses than electrochemistry.

The term electrode can be used in reference to the whole half-cell since it's the site at which the reaction is taking place. At other parts, all we have is storage of reactant and product for the reversible reaction. Consider the Standard Hydrogen Electrode(SHE), the whole half cell is referred to as an "electrode", though this is more convention than technical.

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I suspect the Collins book is for UK A-levels; they should use the clear general definitions; the electrode is the solid metal connecting circuit to non-metallic part, & the electrolyte is the solution of ions:

Here are some additional brief notes on contextual half cell setups:

• SolidMetal/MetalSolution half-cell: Metal Electrode in metal ion solution.

• All AqueousIons half-cell: Platinum electrode in solution.

• Gaseous/AqueousIons half-cell: Glass/Platinum Deliver tube (for gas) bubble into solution.

The salt bridge is an electrolyte; A-level questions on electrode, electrolyte and salt bridge definitions aren't asked too often, consult your spec & exam papers. Importantly, solutions need to be $1dm^3$, at $298K$ and $100kPa$, & salt bridge is typically $KNO_3$