To investigate Electrolysis affecting amounts of substances at Anode+ and Cathode-

Steven Pemberton _ Chemistry Investigation

Prediction

I predict that the longer the electricity is passed through the Anode and Cathode the more effect it will have on them. The anode will be less in weight than the cathode due to it increasing in weight.

Safety

The experiment there are a few safety rules that will have to be taken into consideration. The main safety rule is that when the investigation is taking place the anode and cathode must not be touched in fear of an electric shock. When the investigation is being completed electricity must be turned off with care being careful not to touch anode and cathode together. If anode and cathode were to touch then a spark would appear and a fire may be started or some kind of serious injury may occur.

Method

You will need:

Measuring Cylinder (to measure the amount of ionic solution to use)
An ammeter to record and watch the amps
A 400ml beaker (for the reaction to take place in)
Stopwatch (to time the reaction)
A power pack to supply the electricity for the experiment to take place.
Wires to make a complete circuit.
Two pieces of copper to be the anode and cathode
A holder to hold the anode and cathode
A bulb to use to set up the circuit with

How to do the experiment:

First of all the equipment has to gathered as shown in the list above.
Measure out the ionic solution into the 400ml beaker.
Scrub down the anode and cathode to make it a fair test.
Place the anode and cathode onto the weighing scales separately to take a reading before the investigation ahs taken place.
Next set up the electrical circuit using a bulb where the anode and cathode would be. This is so that the voltage and amps can be set up before the experiment to keep it a fair test. For example:

Then place the Anode and Cathode into the holder and then place all of this into the 400ml of ionic solution.
Remove the bulb from the circuit leaving a gap for the Anode and Cathode.
Place the anode and cathode in the circuit. As shown below:

Now the circuit can be started and timed to take results.

Turn the power of the circuit on making sure the circuit is connected correctly.
Time the experiment for the given amount and turn the power off.
Now disconnect the Anode and Cathode to ...

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Then place the Anode and Cathode into the holder and then place all of this into the 400ml of ionic solution.
Remove the bulb from the circuit leaving a gap for the Anode and Cathode.
Place the anode and cathode in the circuit. As shown below:

Now the circuit can be started and timed to take results.

Turn the power of the circuit on making sure the circuit is connected correctly.
Time the experiment for the given amount and turn the power off.
Now disconnect the Anode and Cathode to weight them.
First though they must be rinsed under the tap to remove any ionic solution on the anode and cathode, which could affect results.
Next dry the anode and cathode on a hotplate for a couple of minutes to dry the anode and cathode.
Now the Anode and Cathode can be measured.
Repeat Steps 8 – 14 for each reading that is needed.

Background

From the study of the Atomic Structure I already know that from the manner in which atoms bond together that electrons play a most important part in the chemical properties of substances. So I should expect electricity (in the form of an electric current) to have some effect on chemical substances when it is passed through it.

I know that hydrochloric acid contains hydrogen ions and chlorine ions. When no current is passing through hydrochloric then the ions are wandering randomly about in the solution as can be seen in the diagram below:

When electricity is passed through the anode and cathode immediately the cathode becomes charged negatively charged and the anode positively charged. The cathode attracts to itself positive ions so in this case the hydrogen ions whilst the anode attracts the negative ions (the chlorine ions). So all the hydrogen ions to the negative pole and negative ions to the positive pole. As can be seen in the diagram below:

Something quite similar happens in the experiment I did but the only difference was that all the copper, which was in the ionic solution, was attracted by cathode and the anode became less in weight meaning that copper must have been removed from the anode.

To help prove and support the results that follow there is the electrolysis laws carried and found by Faraday. Here are a couple of quotes that Faraday stated to do with electrolysis.

Faraday’s First Law of electrolysis states that:

“The mass of any element deposited during electrolysis is directly proportional to the number of coulombs of electricity passed”

This means that the element left on the cathode is corresponding in size to the number of coulombs of electricity passed through the anode and cathode.

Faraday’s Second Law of electrolysis states that:

“The mass of an element deposited by one Faraday of electricity is equal to the atomic mass in grams of the element divided by the number of electrons required to discharge one ion of the element.”

This means that the collection of an element gathered up by one Faraday of electricity is equivalent to the atomic mass in grams of the element divided by the number of electrons needed to absolve one ion of the element.

It has also been discovered that the copper anode releases copper ions and electrons, which form copper at the cathode.

At the anode (+):

Cu® Cu2+® 2e-

At the Cathode (-):

Cu2++ 2e-® Cu

Results

Conclusion

My results show that my prediction is corrected. I predicted that the longer the electricity is passed through the Anode and Cathode the more effect it will have on them. The anode will be less in weight than the cathode due to it increasing in weight. This is correct for the anode but the results show that the outcome for the cathode to be slightly different to the anode. This could be for a several of things. For example the cathode may have been sanded with sandpaper more that the anode. This could have altered the weights making the differences between the cathode and the anode not the same. The results were very accurate and basically obeyed Faradays first and second Laws stating:

Faraday’s First Law of electrolysis states that:

“The mass of any element deposited during electrolysis is directly proportional to the number of coulombs of electricity passed”

This means that the element left on the cathode is corresponding in size to the number of coulombs of electricity passed through the anode and cathode.

Faraday’s Second Law of electrolysis states that:

Really all my results were reasonably accurate with no shocking results. The only that really did keep changing was the amps. This mainly happened due to the apparatus getting hot and went things contain electricity then tend to change readings. For example when thermistor gets hot it fails to disobey Ohms law, which it is designed to do. A thermistor is an electrical component that is sensitive to heat.

Electrolysis is the break up of a compound caused by passing electricity through the molten compound (or a solution of the compound water). Electrolysis can only take place in ionic compounds because covalent compounds cannot and do not conduct electricity when molten or when dissolved in water. Electrodes allow the passage of an electrical current in and out of the electrolyte. The electrolyte is the conducting liquid that undergoes changes when a current passes through it. The electrolyte is copper sulphate solution in my experiment. This is what happened in my investigation. The negative electrode is made out of pure copper but the positive is made out of impure copper. In this process the positive electrode dissolved producing copper ions. Then pure copper was deposited at the negative electrode. The experiment I carried is non-as electroplating. This is a cheap way to coat inexpressive metal with an expensive metal.

Apart from the amps altering automatically as such there was not real problems with the results.

Evaluation

My experiment went well with me results being quite precise. If I were going to do this experiment again I would have to consider changing and altering the equipment to get the best results possible. First of all I would make all my measurements of the chemicals accurate leaving no tolerance, using a measuring cylinder. Then I would clean the equipment to prevent there being any dirt or other chemicals present which could affect the results because the other chemicals can react and alter the resistance of the electricity. This would then give false results. To make the results accurate I will use the same stopwatch and same pieces of cooper for the anode and cathode. Then I would try to time the reactions more carefully keeping an eye on the time so that I know when to stop the reaction. Also I shall use the same electrical equipment to carry out the experiment with. Basically if I carried out the investigation again I would be cautious to make sure all the equipment was the same and that test were carried fair to give very precise results. With the equipment and my results being accurate the investigation went according to plan with no major problems.