EK gen chem reaction at anode

[blackmi4]

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Cd(OH)2(s) +2e- -->Cd(s)+2OH- Enaught=-0.4V
2NiO2(s)+H2O+2e- -->2Ni(OH)2(s)+2OH- Enaught=0.5V

When the nickel-cadmium battery is recharging, what is the reaction at the anode?

Book says the answer is:
2Ni(OH)2(s)+2OH--->2NiO2(s)+H2O+2e-.

Shouldn't the answer be:
Cd(OH)2(s)+2e- -->Cd(s)+2OH-

?

Thank you,

Michael

 

[chenzt]

anode = oxidation, which is losing electrons. Since it is charging, look for a reaction where E is negative and there is a loss of electron.

 

[blackmi4]

Thank you for the reply.

I am certain that the first reaction is the anode. The reduction potential is negative for an anode since it is NOT spontaneous for an anode to gain electrons.

So the first reaction is the anode. The reaction taking place at the anode can only be
Cd(OH)2(s) +2e- -->Cd(s)+2OH- or the reverse of it. Since we are talking about recharging it should be Cd(OH)2(s) +2e- -->Cd(s)+2OH-.

Right?

Thank you!