Daniell cell initial equilibrium

In summary, it seems that when a metal is immersed in a solution of its own ions, it will gain a negative charge. This will create a potential difference between the metal and the solution, depending on the metal's electron-gathering abilities.
  • #1
cianfa72
2,087
231
TL;DR Summary
About the equilibrium reached at Daniell cell electrodes without any external connection
Hello,

consider again a simple Daniell cell with salt bridge in place but no external electric connection between electrodes.

Reading from some source e.g. link1 it seems upon Zinc and Copper metal rods are dipped into their own ions solution, both will gain a negative charge (-) due to an excess of electrons gained inside themselves (metal atoms get oxidised). Having Zinc and Copper different electronegativity, the amount of electrons gained on each electrode will be not the same resulting in a potential difference voltage between them.

From other sources instead (e.g. link2), the Copper rod (Cathode) will behave the other way around: Cu++ ions reduction will take place "stealing" electrons from the Copper rod leaving it positively charged (in other words there will be a depletion of electrons inside the Copper metal rod with an unbalance between protons and electrons inside it)

Which is the truth ?
 
Last edited:
Chemistry news on Phys.org
  • #2
I'm not sure we know. We can measure the potential difference between two electrodes, so if we define the potential of one electrode (0.0V for the standard hydrogen electrode), we can assign electrode potentials to other electrodes. But we can't (I think) measure the potential of a single electrode, so we don't know absolutely how positive or negative the metal is.

I don't think link 2 actually states that Cu becomes positive in the absence of an electrical connection (Cu
2+ is reduced when a current flows); only that Cu is more positive/less negative than Zn. Likewise link 1, at least at the beginning, talks about what happens when a metal is immersed in water (not a solution of its ions).
 
  • #3
mjc123 said:
I don't think link 2 actually states that Cu becomes positive in the absence of an electrical connection (Cu
2+ is reduced when a current flows); only that Cu is more positive/less negative than Zn. Likewise link 1, at least at the beginning, talks about what happens when a metal is immersed in water (not a solution of its ions).
See also here link 3: for Copper osmotic pressure is greater then solution pressure thus the copper electrode will gain positive charge developing a positive potential (even though there is no current flow)
 
Last edited:
  • #4
Any other comment/ideas ? Thanks
 
  • #5
Someone can help me in understanding exactly how really things go ? Regards
 

Related to Daniell cell initial equilibrium

1. What is the Daniell cell initial equilibrium?

The Daniell cell initial equilibrium refers to the state of balance that is achieved when the cell is first assembled and there is no current flow. At this point, the concentrations of the reactants and products are equal, and there is no net movement of ions between the anode and cathode.

2. How is the initial equilibrium of a Daniell cell established?

The initial equilibrium of a Daniell cell is established through the redox reaction between zinc and copper. Zinc metal is placed in the anode compartment and copper(II) sulfate solution is placed in the cathode compartment. Through the oxidation of zinc and the reduction of copper ions, a potential difference is created, leading to the establishment of the initial equilibrium.

3. What factors affect the initial equilibrium of a Daniell cell?

The initial equilibrium of a Daniell cell is affected by several factors, including the concentrations of the reactants and products, the types of electrodes and electrolytes used, and the temperature. Changes in any of these factors can shift the initial equilibrium and affect the cell's overall performance.

4. How does the initial equilibrium of a Daniell cell change over time?

As the cell operates, the initial equilibrium gradually shifts due to the depletion of reactants and buildup of products. This results in a decrease in the potential difference and a decrease in the cell's overall efficiency. The rate of this change depends on the current flow and the concentrations of the reactants and products.

5. Can the initial equilibrium of a Daniell cell be restored?

Yes, the initial equilibrium of a Daniell cell can be restored by either replacing the depleted reactants or by reversing the direction of current flow. This allows the cell to operate again at its initial potential difference and efficiency. However, over time, the initial equilibrium will continue to shift as the cell operates and the reactants are consumed.

Similar threads

Replies
7
Views
2K
Replies
23
Views
4K
Replies
3
Views
1K
Replies
4
Views
2K
Replies
26
Views
4K
Replies
2
Views
1K
  • Chemistry
Replies
5
Views
6K
  • Biology and Chemistry Homework Help
Replies
6
Views
2K
Back
Top