Investigating how the amount of copper affects the mass of the cathode

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INTRODUCTION: In this experiment I will be investigating how the amount of copper affects the mass of the cathode. I will do this experiment twice so that I have an average of my results so that they are accurate. I have already done my preliminary work and from it, I have noticed that I will have to make some changes with the method of my experiment.

AIM: In this experiment, I intend to find out how much copper in the solution affects the mass of the cathode. I will be observing to see what is happening and exactly how much copper is being deposited on the cathode. Out of the four variables that are listed below, I will be concentrating on the time the electrodes are left in the solution and the size of current that will be applied in this experiment.

VARIABLES: There are four variables, which affect this investigation. The first variable is the size of the current applied in the solution. As the current raises so does amount of electrons that are produced on the cathode. This means the anode loses its positively charged ions, which the cathode gains, which means more positive ions, will combine with the electrons on the cathode to produce copper.

The second variable that affects the experiment is the amount of time the experiment is carried out for. The greater the time the electrodes are left in the solution, the more time there is for the copper to be gathered at the anode.

The third variable that affects the experiment is the temperature of the copper II sulphate solution. As the temperature of the solution increases, more of the ions gain kinetic energy and begin to move faster. This enables the positive and negative charged ions to collide faster with the electrodes. As more of the positive and negative ions collide, there is a greater chance for the pure copper to be formed at the cathode.

The fourth variable the affects the experiment is the size of the concentration. The higher the concentration, again the positive and negative ions are more active therefore, there are more chances of collisions at the cathode to form more copper. I will be changing the size of the current throughout my experiment. I will use a rheostat and an ammeter to control the size of the current so that it is adjusted accurately.

BACKGROUND INFORMATION: British scientist, Michael Faraday (1791-1867) is best known for his finding of electromagnet induction and of the laws of electrolysis. Faraday was a son of a blacksmith and was not educated much. Soon he began to read books on electricity and was very interested in electricity. Sir Humphry Davy also employed him as an assistant in his chemical laboratory at the Royal Institution. He was also appointed as the director of the laboratory of the Royal Institution. In 1833 Faraday, succeeded Sir Humphry Davy and became the professor of Chemistry at the Institution.

               .                           Michael Faraday 

                                     

Michael Faraday studied chlorine and discovered the two new chlorides of carbon as well as discovering benzene. The research that established Faraday was magnetism. He investigated the magnetic fields and electromagnet induction. During the same time of his research, Faraday also discovered the two laws of electrolysis. The two laws were: -

(1) The amount of chemical action made by an electric current in an electrolyte is proportional to the amount of electricity passing through the electrolyte.

(2) The amount of substance deposited from an electrolyte by the action of a current is proportional to the chemical equivalent weight of the substance.  

PREDICTION: I predict that in this experiment, the anode will lose its positive ions and the cathode will lose its negative ions. Then after a while, the positive ions will combine with the cathode to produce pure copper whilst at the anode, will dissolve into the solution and provide more copper ions for the cathode to gain and change into pure copper.

 At the end of my experiment, I will accept the cathode to have gained the same amount of mass that the anode has lost. In addition, if I keep on increasing the amount of current that is applied on this experiment, I intend to find an increase of copper, which is formed at the cathode. This should form a straight-line graph where the best-fit line should cross all the points plotted from the results since the size of the current is directly proportional to the mass gained at the cathode. The rate of speed at which the positive ions collide with the cathode should also increase to allow more copper to be formed.

HYPOTHESIS: I will now give evidence to support my theory. If a pair of electrodes are placed into a solution of an electrolyte or in a solution of charged ions, and a source of direct current is applied between the two electrodes, we will see the positive ions in the solution move towards the negative electrode and the negative ions move towards the positive electrode. When the charged ions are reaching the electrodes, the ions in the solution may loose or gain electrons and are changed into neutral atoms. The reaction at the electrode depends on the voltage that is applied.

        Here is an example of what I expect to happen in this experiment. When the solution of copper sulphate has dissolved in water, it divides into positive copper ions and negative sulphate ions. When the voltage is applied to the electrodes, the positive copper ions move towards the negative electrode, are discharged, and are deposited on the electrode as metallic copper. The negative sulphate ions move towards the positive electrode and are discharged and combined with the water of the solution. The black sludge that is left at the bottom is the impurities of the copper. This decomposition by an electric current is best known as electrolysis. This experiment also follows the laws of electrolysis that Michael Faraday discovered. The two laws are:

(1) The amount of chemical action made by an electric current in an electrolyte is directly proportional to the amount of electricity passing through the electrolyte.

In addition, if we wanted to find out how much electricity is passed through the electrolysis experiment, we would use this formula. If a current of 1 amp (A) flows for 1 second (s) the amount of electricity passed is 1 coulomb (c). During an experiment, it is found that because a large number of coulombs are passed, it is better to work out the amount of electricity passed in units of Faraday’s.

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1 Faraday (F) = 96500 coulombs (approximately)

Amount of electricity passed = current (A) x time (s)

                                                        96500 (1 F)            F

It is found that the amount of electricity passed determines the mass of products formed.

        

(2) The masses of different elements liberated by the same amount of electricity form simple whole number ratio’s when divided by their relative atomic ...

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