Tom C

Abstract
My experiment is making a galvanic cell with ascorbic acid, acetic acid and Acetylsalicylic acid and then measuring the electricity in volts and amps. Acetic made the best cell.
Introduction
The Galvanic cell was named after Luigi Galvini. Galvanic cell is when you put Copper and Zinc into an acid to create an electric current. The way this works is that Zinc attracts electrons and Copper repels them creating a flow of electrons. The reaction that happens here is called an oxidation-reduction (redox) reaction. The definition of this is: “Any chemical reaction which involves oxidation and reduction.” (Chemistry.about.com).Oxidation is the loss of electrons, so the Copper would oxidize. Reduction is the gain of electrons so the Zinc would go threw reduction. So what is happening is that the Zinc wants electrons, the Copper doesn’t. The Zinc takes in the electrons and reduces. The Copper would oxidize. Cells are created whenever two different metals connected in some way are put in a conductive fluid. This is basically how a real battery works. However in a real battery a stronger acid is used making for a much better reaction between the three chemicals. Also, in a real battery many sheets of different metals to make a bigger electric current in a smaller area.
My testable question for this experiment is: What acid will make the best cell, acetic acid or vinegar (HC3H3O2), ascorbic Acid or vitamin C (C6H8O6), or acetylsalicylic acid or aspirin (HC9H7O4) at 2.5 percent concentrations using Zinc and Copper as electrodes. Best cell will be measured as the cell that creates the most electricity (in volts and amps). My hypothesis is that the acetylsalicylic acid will make the most electricity because it has lots of atoms and lots and lots of electrons. And so more electrons mean more electricity going threw the wires.
Materials and Methods
1. Acetic Acid (2.5% solution) from Vinegar
2. Ascorbic Acid (2.5% solution) from Vitamin C
3. Acetylsalicylic Acid (2.5 solution) from Aspirin
4. 2 Galvanized Nails (Zinc coated nails)
5. 1 Penny (Copper coated coins)
6. Copper wire (approximately 1 ft)
7. Voltmeter (device that measures electricity in volts)
8. Ammeter (a device which measures electricity in amperes)
9. Cardboard
10. Mortar and Pestle
The first thing that I must do is calculate the amount of acids that must go into the water to dilute it to 5% concentration. The Acetic acid is all set because it comes as a 2.5% solution from the store. For the aspirin and the vitamin C I will use a ratio of water and the acid to find to proper amount to mix with it. 100Ml of water has a mass of 94 grams (which I determined experimentally). I divided this 100 mL by 2 to get 50 mL of water, and then I divided the mass by 2 and got 47. 47 multiplied by .05 (the percent concentration) is 2.35. This means I need 2.35 g of aspirin. 2.35 divided by the amount of aspirin in one pill (325 mg) is 7.23. That’s how many tablets of aspirin I need in 100ml of water. So 2.35 (amount in grams of Vitamin C that I will need) divided by .5 (amount of grams in 1 tablet of Vitamin C) is 4.7. That’s how many tablets of vitamin C I will need.
The next thing that I will do is hook the nails and pennies to the wires. I will take 2 separate lengths of non insulated copper wire and wrap it around each of the metals I will then prepare the cells by putting the two electrodes and suspending them in the acid. After that I will measure the electricity by using an ammeter and a voltmeter. The voltmeter measures electricity in volts while the ammeter measures it in amperes. I will record each result only one time on a table. After that I plan to put this data in a graph. Throughout this whole processes I will be taking pictures to prepare for my presentation. Volts and Amps are units used to measure electricity.
Results
Acetic acid created the most measurable electricity at 1 volt 2 amps. Asetylosicylic acid created the second most measurable electricity at .5 volts and 2 amps. Thirds was the Ascorbic Acid at .3 volts and 1.5 amps.

Acid Electricity
Ascorbic Volts: .3 Amps: 1.5
Asectylosicylic Volts: .5 Amps: 2
Acetic Volts: 1 Amps: 2
untitled.bmp

Discussion

My hypothesis was proved very wrong. I thought that the Acetylsalicylic acid would generate the most electricity and therefore produce the best cell. The acetic acid however generated the most electricity and created the best cell. This experiment proves that acetic acid produces the most electricity. I have some theories on why acetic acid produces the most electricity. One theory is because it is more acidic than the other two acids. This means that it has a lower pH than the others: Vinegar (acetic acid) has a pH of 2.4. Ascorbic Acid has a pH of 5.5, and Acetylsalicylic acid has a pH of 3.4. The more acidic it is the stronger electrolyte it is. The stronger the electrolyte, the more it ionizes in an aqueous solution. The more it ionizes, the better it is at conducting electricity (Zumdahl, 136). Therefore stronger acids are better electrolytes. From Rose-Hulman.edu I found that the amount of electricity generated has to do with the conductivity of the acid. Conductivity means how much electricity something is able to conduct. So the better the electrolyte the more electricity the cell will generate. And since the stronger the acid the better the electrolyte the stronger acid will make a better cell.

In the future I would do this experiment with stronger acids like hydrochloric acid or sulphuric acid. Then I could prove my theory that the more acidic a substance is, the better electrolyte and therefore better conductor it makes. I designed it well so it all went very smoothly and was completed within two days.
There were a few possible sources of error. For one my calculations could have been wrong. Second I noticed that it was hard to find out how to do the tenths of a gram accurately, although I think that I was close. Also I noticed that some of the chemical was left in the mortar and pestle I used. Also I noticed that some of the chemical refused to dissolve with the water leaving some sludge at the bottom of the cup. I think that this would affect my experiment by it not being as strong or as weak as it might be normally. Also I left them out over night. I'm not worried about evaporation because they were out there for the same time. However I think that the time would weaken the acids. Each one of those errors was relatively minimal except that if they all happened then it could add up to a big error.

Zumdahl Chemistry 6th edition Boston Houghton Mifflin

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