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# [HALF CELLS] What happens to the cell potential when water is added to one cell? Watch

1. The whole question is "when water is added to the chromium half cell, the cell potential changes. Suggest one reason for this observation".
The other half cell is Cd, chromium has a more negative E cell value than Cd.

I want to know how water affects it and why. Then I can answer the question myself. (: thanks!
2. (Original post by eggfriedrice)
The whole question is "when water is added to the chromium half cell, the cell potential changes. Suggest one reason for this observation".
The other half cell is Cd, chromium has a more negative E cell value than Cd.

I want to know how water affects it and why. Then I can answer the question myself. (: thanks!
Look up the Nernst equation. This shows you the effect of concentration (and temperature) on cell potentials ...
3. I think what the question wants you to discuss the fact that the chromium (or whatever they are) ions are aqueous.

If you add more water to the half-cell you are decreasing the concentration of the (aq) ions.
If the Equation is Cr3+(aq) + 3e- ⇌ Cr(s) EO:-0.74

by adding water to the half-cell you:
• Shift the position of the equilibrium to the LHS because the Cr3+(aq) conc. has decreased
• This result in a 'more negative' electrode potential of the Cr half cell

not sure if the above is correct but that is what I would guess.
EO is supposed to be the symbol for electrode potential :P
4. (Original post by freetown)
I think what the question wants you to discuss the fact that the chromium (or whatever they are) ions are aqueous.

If you add more water to the half-cell you are decreasing the concentration of the (aq) ions.
If the Equation is Cr3+(aq) + 3e- ⇌ Cr(s) EO:-0.74

by adding water to the half-cell you:
• Shift the position of the equilibrium to the LHS because the Cr3+(aq) conc. has decreased
• This result in a 'more negative' electrode potential of the Cr half cell

not sure if the above is correct but that is what I would guess.
EO is supposed to be the symbol for electrode potential :P
Thanks! Perfect explanation.

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