Electrochemistry (Remote)
VIDEO LINKS:
Lab Experiments (Write protocols and perform experiments based on these):
Part 1 (The preparation and electrolysis of one of the indicator solutions is required) Part 2 Part 3Data analysis and calculations (Use these if you need help with your data and calculations)
- Introduction to electrochemist
- The electrochemistry experiments:
The prelab must include Experimental Protocol, Chemical Table and Equipment Table.
The lab report requires all sections (including prelab sections) to be completed in one document.
Experimental Protocol
(Analysis) Watch the experiment videos. Take notes on the protocol. Stop the video and re-watch as necessary to acquire the details of the procedure. Write out the protocol for each part of the experiment. (It can be written in sequential steps. Complete sentences are not necessary.) This is the protocol you will follow, so be detailed.
Chemical Table
(Representation) Prepare your chemical table including the materials you will use in the experiment. Here is a general template that you may use.
| Chemical Name | Chemical Formula | Molar Mass (g/mol) | Hazards | Reference | PPE |
| Sodium Chloride | NaCl | 58.5 | Skin irritation | https://fscimage.fishersci.com/msds/21105.htm | |
Equipment Table
(Analysis) Identify the equipment (type AND size) needed for the experiment and include the name and an image of each. Be sure to describe the equipment, how to use it, and why it is suitable for this use.
| Equipment Name | Equipment Picture | Intended Purpose |
Data Collection
(Acquiring competencies) Following your detailed protocol based on the videos, perform all the experiments. Record your observations and take pictures of your key steps in the process. Your observations and images need to be incorporated in your data section and this section should be as detailed as possible as you will use this information to complete your discussion.
Data Processing
Part 1: Electrolysis of an Indicator Solution
- (Analysis) Describe the color of the indicator around each electrode and identify the chemical species responsible for the color.
- (Representation) Write the chemical equation for the dissociation of NaCl.
- (Representation) Write the half-reaction that occurs at the anode.
- (Representation) Write the half-reaction that occurs at the cathode.
- (Representation) Draw the diagram for the electrolytic cell in this experiment, indicate the direction of the electron flow and label the electrodes.
- (Existing knowledge, research and views) Present the standard electrode reduction potentials for the half reactions at the anode and cathode.
- (Assumptions and Analysis) Fill in the following table using the observations and data from your experiments.
| Assumptions made | Testing the assumption | If assumptions are wrong ... |
|---|---|---|
| Oxygen is produced in the gas phase. | Bubbles will be visible. | No bubbles... |
Part 2: Making a Potato Battery
- (Experimental design) Select a variable (temperature, pH, type of fruit, type of vegetable, etc.) that you will study as a team. Each team member will then select a different condition of the variable (e.g., apple instead of potato) and create a new battery. Write a detailed protocol. Show pictures of the new batteries under different conditions with the student inventor in the frame.
- (Representation) Write the overall reaction that occurs.
- (Representation) Draw the diagram for the galvanic cell in this experiment, indicate the direction of the electron flow and label the electrodes.
- (Assumptions and Analysis) Fill in the following table using the observations and data from your experiments.
| Assumptions made | Testing the assumption | If assumptions are wrong ... |
|---|---|---|
| Electrons flow more easily without cell walls. | Repeat experiment with cooked vegetable. | Same or less current will flow. |
Part 3: Making a Voltaic Pile
- (Representation) Write the half-reaction that occurs at the anode.
- (Representation) Write the half-reaction that occurs at the cathode.
- (Representation) Write the overall reaction that occurs.
- (Existing knowledge, research and views) Present the standard electrode reduction potentials for the half reactions at the anode and cathode.
- (Manipulation) Calculate the standard cell potential (E°cell) at 25 °C using the half-cell potentials.
- (Manipulation) Calculate the ΔG° using the formula: ΔG° = - n × F × E°cell.
- (Interpretation) Classify your reaction as spontaneous or non-spontaneous.
- (Assumptions and Analysis) Fill in the following table using the observations and data from your experiments.
| Assumptions made | Testing the assumption | If assumptions are wrong |
|---|---|---|
| The voltaic pile only works with copper and zinc. | Combine other metals in similar sequence. | There will be current detected. |
Discussion
Write a minimum one-page discussion (12-point font, single-spaced) on the experiment conducted this week. Address at least one question in each category as fully as possible by integrating the collected data, providing explanations for the observed trends, and evaluating whether your original assumptions about the experiment were validated by the results.
The assignment will be graded on completeness, clarity of the explanations, and the meaningful integration of the collected and calculated data.
Correct grammar and appropriate formatting for chemical formulae and chemical reactions are expected.
- Interpretation) Classify the reactions observed in these experiments and provide a supported argument for your choice.
- (Existing knowledge, research, and views) Define galvanic cell, electrolytic cell and voltaic cell. Give an example for each from your experiments.
- (Existing knowledge, research, and views) Define the half-cell, and describe how they work using one of these experiments as supporting evidence.
- (Existing knowledge, research, and views) Describe the relationship between the half-cell potential and the cell potential. Use your experiments as supporting evidence. (Include the units, why some potentials are positive and some negative, and the information gleaned from those numbers.)
- (Analysis) A galvanic cell has a barrier between the anode and the cathode, whereas the electrolytic cell does not. Evaluate whether it is possible to have a galvanic cell without a barrier and provide a supported argument for your selection.
- (Analysis) Describe what happened to the color of the indicator solution when the electrolysis started and provide an explanation for your observation.
- (Analysis) Describe what happened to the color of the indicator solution when the electrodes were removed from the Petri dish and provide an explanation for your observation.
- (Analysis) Define the role of the pencil lead, the NaCl and the water in the electrolysis experiment. Identify at least one substitute for each required material.
- (Analysis) Describe the role of the mat board in the pennies experiment. Describe the purpose of the salt and vinegar soak.
- (Analysis) The anode and the cathode were separated in each experiment. Provide a supported argument for why they were never in contact with each other during the experiments.
- (Existing knowledge, research, and views) Describe what metals are used in the manufacture of the penny and the galvanized nail.
- (Existing knowledge, research and views) Compare the sign of the Gibbs free energy of the electrolytic cell to that of the galvanic cell.
- (Analysis) Only the electrolysis experiment required a battery. Provide a supported argument for not using a battery when making a voltaic cell.
- (Analysis) Compare the results obtained from your team experiment. Describe how modifying the selected variable impacted the performance of the resulting battery.
- (Assumptions and limitations) Car batteries run at a minimum of 12.6 V. What would have to be true for a potato battery that generates sufficient voltage to replace your car battery? Provide a supported argument for your choice.
- (Manipulation) Assuming a potato costs thirty-three cents and can generate 0.5 volts, calculate how many potatoes, and at what cost, would be needed to run and generate 110 volts. Show your calculations.
- (Assumptions and limitations) What would have to be true for your 110 V potato battery to become a suitable replacement for one of the electrical outlets in your house? Provide a supported argument for your choice.