Electrochemistry Question, Galvanic/Daniel Cell

In summary, a simple setup was used with high school students, consisting of a zinc plate and copper plate connected to a speaker, with filter paper soaked in ZnSO4 and CuSO4 on either side and separated by cellophane in a Petri dish. A black substance was observed to build up on the base of the zinc plate, potentially copper reduced from the copper plate. The presence of current flowing through the setup suggests that ions are passing through the cellophane.
  • #1
mannioc3
2
0
Using a very simple set up with high school kids,

Zinc Plate
*on*
Filter paper soaked in ZnSO4
*on*
cellophane
*on*
Filter paper soaked in CuSO4
*on*
Copper Plate
*in*
Petri Dish

Copper and zinc plate connected to a speaker. I know the process involved and the equations. Not using a salt bridge. After a while on the base of the Zinc plate there is a build up of a black substance and for the life of me i can't tell what it is.
Any ideas what it is?
 
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  • #2
I won't be surprised if it is copper reduced on zinc. It doesn't have to be red, at least not initially.
 
  • #3
Where does the copper come from?
The cells are separated by the cellophane... how would the copper reduce and percipitate UP onto the zinc plate? is this possible?
 
  • #4
If there is current flowing, it means ions pass through the cellophane, there is no other way.
 
  • #5


The black substance that builds up on the base of the zinc plate in this setup is most likely copper (II) oxide (CuO). This is formed through a redox reaction between the zinc and copper ions in the solution. As the zinc loses electrons and is oxidized, the copper ions in the solution gain those electrons and are reduced, forming solid copper (II) oxide on the surface of the zinc plate. This process is known as galvanic corrosion and is a common occurrence in electrochemical cells. It is important to regularly clean the plates to maintain the efficiency and accuracy of the cell.
 

1. What is an electrochemical cell?

An electrochemical cell is a device that converts chemical energy into electrical energy through redox reactions. It consists of two electrodes (anode and cathode) connected by a conductive electrolyte solution.

2. What is a Galvanic/Daniel cell?

A Galvanic cell, also known as a Daniel cell, is a type of electrochemical cell that uses a spontaneous redox reaction to generate electrical energy. It consists of a zinc electrode (anode) and a copper electrode (cathode) connected by a salt bridge and immersed in an electrolyte solution.

3. How does a Galvanic/Daniel cell work?

In a Galvanic cell, the zinc electrode (anode) oxidizes, releasing electrons into the electrolyte solution. These electrons flow through the external circuit to the copper electrode (cathode), where reduction occurs. The ions in the electrolyte solution complete the circuit by flowing through the salt bridge. This flow of electrons and ions creates an electrical current.

4. What is the purpose of a salt bridge in a Galvanic/Daniel cell?

A salt bridge is a tube filled with a salt solution (usually KCl) that connects the two half-cells in a Galvanic cell. It allows ions to flow between the two half-cells, completing the circuit and maintaining charge balance. This prevents the buildup of excess charge, which can disrupt the cell's operation.

5. How is the cell potential of a Galvanic/Daniel cell calculated?

The cell potential, or voltage, of a Galvanic cell can be calculated using the Nernst equation: Ecell = E°cell - (RT/nF)ln(Q), where Ecell is the cell potential, E°cell is the standard cell potential, R is the gas constant, T is the temperature in Kelvin, n is the number of electrons transferred in the redox reaction, F is Faraday's constant, and Q is the reaction quotient. The more positive the cell potential, the greater the likelihood that the cell will produce electricity.

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