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Homework answers / question archive / CHE-122: Principles of Chemistry II Laboratory 6 Procedure: Electrochemistry: Galvanic Cells and the Calculations of Cell Potential Background: Galvanic cells, also called voltaic cells, or battery cells are type of electrochemical cells that in which spontaneous reaction generates an electric current
CHE-122: Principles of Chemistry II
Laboratory 6 Procedure: Electrochemistry: Galvanic Cells and the Calculations of Cell Potential
Background:
Galvanic cells, also called voltaic cells, or battery cells are type of electrochemical cells that in which spontaneous reaction generates an electric current.
Here there is an example of spontaneous red-ox reaction that is used in a galvanic cell:
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s)
we can separate above equation in two half-reactions:
Zn(s) → Zn2+(aq) + 2e
and
Cu2+(aq) + 2e → Cu(s)
As shown in Figure 1. potential, a voltage difference between two half cells, drives electric current.
A Galvanic cell consists of:
Two electrodes, made of metal or graphite, placed in two separate containers (half-cells):
-anode: oxidation process occurs there, has higher potential so electrons flow away from it.
-cathode: reduction process occurs there, has lower potential, electrons flow toward it.
Salt bridge: made of porous get that connects two half cells, only counter ions can flow through it from one solution to another.
Figure 1: Zinc-copper galvanic cell.
Instead of drawing the diagram, we use the following electrochemical cell notation to describe zinc-copper galvanic cell:
Figure 2. Electrochemical cell notation for zinc-copper galvanic cell.
Each half-cell has its own potential. The standard potential of the cell Eocell is the resulting potential from combining the potential of each half-cell. Calculation of the standard cell potential can be conducted using either of two methods described below.
First method requires combining half-reaction and their standard electrode potential values, reduction and oxidation.
Second, involves the equation that calculate the difference between standard reduction potentials:
E°cell = E°cathode + E°anode
Figure 3: Formula Used for Calculation of Any Cell Potential Applying the Standard Electrode (Reduction) Potentials –see textbook Table 19.1 p 652.
There are few of objectives of this lab:
Before you start this laboratory assignment, you are encouraged to review Section 19.2-19.5 on pages 642-656 in the textbook. Throughout this laboratory assignment, you will be required to analyze an electrochemical reaction in terms of electrons exchange. Be sure to record all observations and any relevant notes that you think you will need to include in your laboratory report.
Take a moment to formulate and write down a hypothesis describing what causes formation of the electric current in a galvanic cell?
Answer the following questions in at least 5-10 sentences.
Preparing the Lab 6
Analyzing the Data
anode, cathode, salt bridge, direction of the electric current flow
This section should include notes about any observations or data collected during the lab.
Report Requirements
This section contains key information that must be included in your typed report.
Note: All reports will be graded using the rubric embedded within the course.
Here are some questions to consider as you write your report:
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