Question

How to identify the electrolyte of a cell/saltbridge with only the half equation and ionic equation of the cell?
For instance,
\(Pb(s)\longleftrightarrow Pb^{2+}
(aq)+2e^{-}\)
\(Fe^{3+}
(aq)+e^{-}
\longleftrightarrow Fe^{2+}
(aq)\)
Balanced net ionic equation for overall of cell reaction:
\(Pb(s)+2Fe^{3+}
\longleftrightarrow Pb^{2+}
(aq) +2Fe^{2+}
(aq)\)

Answer 1

I'm not sure if this helps.
For electrolyte, it changes from the element/compound to its ions. For salt bridge, the original compound/element should be in ionic form (should be an ion, you may say). In your case, is Fe^3+ the salt bridge and Pb the electrolyte?

Answer 2

well Fe^3 +e^- ....
is reduction..so its an oxidant..that is not part of the salt bridge or electrolyte..they are half equations; from my understanding.

and the answer for the electrolyte for the example above is KNO_3 but there's no explanation; so i dont understand how and why

do you by chance know?

Answer 3

Blah... Sorry that I think I read the question wrong! For exam purpose, I just memorize them case by case. I think it's quite hard to identify the right electrolyte and salt bridge used just from the given equation of reaction. But it's important to know that ions in salt bridge and electrolyte should not participate in the redox nor react with the reactants in the redox reaction. Perhaps that's the reason why it is chosen. Sorry again that I can't help you!

Answer 4

Ok thanks.

Answer 5

KNO3 is often the electrolyte of choice for the salt bridge because the nitrate ion won't precipitate other metal ions, and the reduction of potassium is highly unlikely unless the cathode of the cell has an even larger negative potential.