Explore Electrochemistry: Building a Galvanic Cell, Reverse the Flow, Merging the Half-Cells, and Beyond the Bench

 

What is electrochemistry?

Building a Galvanic Cell 

My expectation of Galvanic Cell: 1.044v

The observed voltage of 1.044v in the galvanic cell fits my expectation because the value is the standard reduction potential of zinc and copper in a specific way, copper ions should be reduced at the cathode, and Zinc atoms should be oxidized at the anode. 

When the salt bridge was removed from the galvanic cell, there was a decrease in voltage and the copper electrode turned brownish with this observation, I was able to realize that the salt bridge plays an important role between two cells to more charged particles. Copper ions cannot be removed by removing the bridge so that it presents a brown color. 

Electrodeposition occurs when the material is deposited during an electrochemical process. Electrostripping occurs when a material is stripped during an electrochemical process. Based on your observations and knowledge of galvanic cells, identify each electrode type (anode or cathode) AND determine which process occurred (electrodeposition or electrostripping). 

Electrode: Zinc

Type: Anode

Process: Electrostripping

Half Reaction: Zn (s) --> Zn 2+ + 2e-

Electrode: Copper

Type: Cathode

Process: Electrodeposition

Half Reaction: Cu 2+ +2e- -> Cu (s)

Reverse the Flow

1. The voltage of the galvanic cell with the penny in place of the copper wire. How it compares to deviates from the galvanic cell. 

Comparing to the cottage from the galvanic cell, that with the penny in place of copper wire is much lower, which was 0.92 v because of the penny, it presents lower voltage when we put penny over the copper wire, it acts as a galvanic cell, its zinc core acts as anode while its copper acts as cathode, which made penny contributes less voltage to the overall cell. Consequently, placing penny on copper withe affects the surface area of electrodes, which leads to lower cottage of the cell. 

2.  The Voltage of the reversed cell with the 9 V battery. Briefly explain how it compares to deviates from the galvanic cell

Comparing to galvanic cell, the voltage of reversed cell with 9v battery was reassured as -8.8v it results much more negative result. The reason for this measurement is that 9v battery forces the electrocutions to flow. Therefore, the copper ion are dissolved onto zinc electrodes, leading to negative voltage.  

3. Observations of the penny after being in the non-spontaneous electrochemical cell

The Penny after being in the non-spontaneous electrochemical cell underwent a process of disintegration where the copper cation on the surface dissolved into zinc electrode. Therefore, the penny became dull and tarnished. Moreover, the mass decreased from 2.437g to 2.432g. The penny's surface showed erosion because of dissolution of the copper ions. 

4. Considering the mass of the penny, quantitatively describe wheter it changed a significantly measurable amount

1. After putting the penny in the non spontaneous electrochemical cell and washed in PI water, the mass changed from 2.437g to 2.432g . We can say this amount of change is not that big influence so that can be just an experimental error. 

2. After sitting in call2 solution, the mass -f penny decreased to 2.432; which also cannot be said a big change in this reaction. Therefore, this cannot be significant chemical changes during experiment. Consequently, the mass of penny did not change enough to be significant.

Determine the half-reaction for the species deposited or stripped on each electrode

Electrode: Zinc

Type: Cathode

Process: Electrodeposition

Half Reaction: Zn 2+ + 2e- -> Zn (s)

Electrode: Copper

Type: Anode

Process: Electrostripping

Half Reaction: Cu (s)- -> Cu 2+ + 2e- (s)

Merging the Half-Cells

1. Explain what happed when the penny was soaked in the copper solution

* This process ONLY works for pennies after 1983. Prior to 1982, pennies were solid copper. 

When the penny was soaked in copper solution, electroplating would be occurred, which only applies to pennies made after 1982 because they put mostly zinc with copper coating. During experiment, the copper coating was taken off by acidic solution, which leaves zinc core. Then copper ions were deposted on to surface of penny that creates a new copper layer. On the other hand, this layers would be darker with less shine than original coating. This can be explained with various color and reflecting of the penny itself. In conclusion, the experiment presents how electroplating can be used to coat a metal object with a thin layer of another metal. 

2. Report your observations of the penny before and after being in electrical contact with Zn in the ZnCl2 electrolyte solution

Before being in electrical contact with Zn in ZnCl2 electrolyte solution, the penny had shining copper surface while the penny becomes silver after redox reaction. This can be explained by losing elections of copper atoms which transfer into Zn ions then it forms layer of zinc on penny's surface while the copper was dissolved as Cu 2+ ions. 

This reaction happened spontaneously; it was only heated to make it happen during the course of the lab rather than over a few days. Based on your observations and knowledge of spontaneous electrochemical reactions, identify each electrode type (anode or cathode) AND determine which process occurred (electrodeposition or electrostripping). Furthermore, determine the half-reaction for the species deposited or stripped on each electrode.

Electrode: Zinc

Type: Anode

Process: Electrostripping

Half Reaction: Zn (s) --> Zn 2+ + 2e-

Electrode: Copper

Type: Cathode

Process: Electrodeposition

Half Reaction: Cu 2+ +2e- -> Cu (s)

1. When you merged the Zn and Cu electrodes into the ZnCl2 electrolyte, a spontaneous change did occur (so this is a galvanic cell). However, the reaction would fairly quickly stop. Explain why

The Zn metal will be consumed until no longer available to react, that ends the reaction rapidly. The galvanic cell will stop making voltage after all Zn used. 

2. Finally, when you heated the penny in part C directly on the hotplate, explain what happened from the molecular perspective. The word “alloy” may be useful to know.

On a hot plate, the thin copper coating on the surface of heated Penny reacts with oxygen in the air, which forms CuO. The tiny black spots would be appeared on the surface which makes two different layers. As such, it cannot be said on alloy but some of the us pennies were made of alloy ( copper & zinc )

Beyond the Bench 

In Part A, you explored how to construct a battery. In Part B, you explored how to reverse and “recharge” a battery. In Part C, you explored the challenges of trying to reduce the size of battery from two electrolytes, two electrodes, and a salt bridge into one electrolyte that also serves as a salt bridge to the two electrodes. All of this is to say (1) batteries are incredible and (2) the size of batteries that we use are-impressive. However, we are still searching for better batteries. Perform some research and propose at least three ideas on to further reduce the current size of battery technologies.