What happens in an anode and cathode half reaction?

Expert Answers

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In order to fill in the missing parts in the problem, first, we need to identify each of the following species in the system.

  • Anode - is the electrode where oxidation happens
  • Cathode - is the electrode where reduction happens

To avoid confusion, cathode reaction is always drawn as the right electrode while the anode is the left electrode. Having said that, 

  • Anode - `Ni _((s))`
  • Cathode - `Cu _((s))`

What happens in both electrodes?

  • Anode half-reaction

`Ni(OH)_2 _(s) + 2e^(-) hArr Ni _((s)) + 2OH^(-)`

  • Cathode half reaction

`Cu(OH)_2 _(s) ++ 2e^(-) hArr Cu _((s)) + 2OH^(-)`

For the line notation:

`Ni _((s))|Ni(OH)_2 _(s) |KOH _((aq))|Cu(OH)_2 _(s) |Cu _((s))`

Anode half reaction is written on the left part and the cathode half reaction on the right side. 

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