Question

Look at all the interfaces of a Daniell Cell. Assume an open circuit (what is that?) and describe the equilibrium at each interface (Terminal-Electrode-Solution-Solution-Electrode-Terminal). Derive an equation for the voltage of the cell that takes in account all the values that determine each of the equilibria (which do not cancel). Which cancel nearly? Why? When not? I saw a previous identical question of this and the person didn't answer what was asked. What is really important here that I need to know is, how to derive the equation and I shown to me every step of it, so what occurs from each step in deriving the equation from 1 terminal to the next(including all steps inbetween). IUPAC Cu’|Zn|ZnSO4(aq) CuSO4(aq)|Cu|Cu”. Each of these steps to show equation derivation.

Answer 1

An open circuit means that the electrons move throgh a conductor from the anode to the catode, and a saline bridge stabilize the charges between both, as shown in the diagram.

This means how the cell is built: Cu’|Zn|ZnSO4(aq) CuSO4(aq)|Cu|Cu” ; Cu as conductor, an elctrod of Zn inmerse into a solution of ZnSO4; a solution of CuSO4 with a Cu electrode, and there also shoud be two bars (||) between both elctrodes which means a saline bridge.

To determine the equilibrium you need to separete the reactions occuring in the anode and the catode.

In the Daniell cell, copper and zinc electrodes are immersed in a solution of copper sulfate and zinc sulfate respectively.

At the anode, zinc is oxidized per the following half reaction:

At the cathode, copper is reduced per the following reaction:

By adding both half reactions you get the general equilibrium reaction, and you eliminate the electrons from the reactions (for cancel the electrons you need to have the same number in both half reactions, and they should be in opposite sites of the reaction, like in this case you have two in the left side for the Cu and 2 in the right side for the Zn).

The E⁰ means the standard reduction potential or voltage for each half reaction, you can find them in tables in any chemistry book, to get the overall standard potential for the the global reaction you need to use

You do not need to derive the equation since it is already given as shown above.