Galvanic cells - product and reactant

[sbuxaddict]

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Hi everyone,

For galvanic cells, the TBR book says to increase the voltage in the cell you can either increase the concentration of ions in the cathode solution or decrease the concentration of ions in the anode solution. It cites Le Chatelier's principle, saying that increasing reactants/decreasing products will make the reaction go forward.

Why are the cations/ions in cathodes considered reactants? I would have thought they were products, because the anodes eventually dissolve and the cathodes get plated, ending the reaction.

 

[BB8730]

This can be a confusing concept, but it helps to look at the half reactions.

Anode
Zn(s) -> Zn2+(aq) + 2e-

Cathode
Cu2+(aq) + 2e- -> Cu(s)

As you can see, the Cu2+ ions are the reactants at the cathode but the Zn2+ ions are the products at the anode. Increasing the ion concentration at the cathode or decreasing it at the anode would pull the reaction forward.

Why are the cations/ions in cathodes considered reactants? I would have thought they were products, because the anodes eventually dissolve and the cathodes get plated, ending the reaction.

The cathodes get plated with solid species - the aqueous ions are the reactants.

 

[sbuxaddict]

This can be a confusing concept, but it helps to look at the half reactions.

Anode
Zn(s) -> Zn2+(aq) + 2e-

Cathode
Cu2+(aq) + 2e- -> Cu(s)

As you can see, the Cu2+ ions are the reactants at the cathode but the Zn2+ ions are the products at the anode. Increasing the ion concentration at the cathode or decreasing it at the anode would pull the reaction forward.

The cathodes get plated with solid species - the aqueous ions are the reactants.

Ohh got it, when the equations are separated it makes so much more sense.
Thanks!