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Electrolysis - The aim of this experiment is to prove that by passing electric current through an aqueous copper sulphate solution changes the mass of each electrode. The anode's mass will increase and the cathode's mass will decrease.

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Introduction

Solids, e.g. metals conduct electricity; the current is carried by electrons. The battery forces the electrons through the conductor. The metal may change for example it may become hot, but when the flow of current is stopped the metal is just as it was before. When a metal conducts electricity no chemical reactions occur. However when a molten salt conducts electricity, chemical changes occur, and new substances are formed. This diagram shows an experiment, which aims to find out what happens when a direct electric current passes through a molten salt. A salt is a compound of a metallic element with a non-metallic or elements. Lead (II) is a salt with a fairly low melting point. The container through which the current passes is called a cell. The rods, which conduct electricity into and out of the cell, are called electrodes. The electrode connected to the positive terminal of the battery is called the anode. The electrode connected to the negative terminal is called the cathode. The electrodes are usually made of elements such as platinum and graphite, which do not react with electrolytes. When the salt melts, the bulb lights, showing that the molten salt conducts electricity. At the positive electrode (anode), bromine can be detected. It is a reddish-brown vapour and therefore a non-metallic element with a very pungent (safety- the vapour produce must not be inhaled). At the cathode (negative electrode), lead is formed. This can been seen after cooling. Lead Bromide (II) has been split up by the electric current, it has been electrolysed. Electrolytes are the compounds, which conduct electricity. Bromine is negatively charged and only goes to the positive electrode and Lead is positively charged meaning is only goes to negative electrode. These charged particles are called ions. Positive ions are called cations because they travel to the cathode and negative ions are called anions because they travel to the anode. A bromide ion, Br- differs from Br a bromide atom because it has one more electron. ...read more.

Middle

Q=IT Charge = Current x time Equation for Faraday's 1st Law Faraday's 2nd Law The masses of different substances produced by the same current in the same time are ? to their atomic masses divided by their ionic charges of valencies. The aim of this experiment is to prove that by passing electric current through an aqueous copper sulphate solution changes the mass of each electrode. The anode's mass will increase and the cathode's mass will decrease. I will also attempt to investigate the relationship between the amount of change and the size of the voltage and current. If Faraday's laws are correct the mass gained at the anode will equal the mass lost at the anode. From my research I can predict that the Cathode will increase in mass and the Anode will decease in mass. I think that the higher the voltage the larger the change in mass will be, because with more volts passing through the electrons they move around more and therefore more electrons move to the cathode and more electrodes leave the anode. I can also predict that an increase in time and therefore and increase in the length of time the current flows will increase the change in mass. I also think that if the time doubles the amount of copper produced will also double baring mind that if the time doubles the charge doubles. * Power Pack * Two pieces of copper * Stop Clock * Copper sulphate solution * Accurate balance * I will be working with electricity for the main, which is as a high voltage so I will be careful in order to remain safe. * I will also be working with a power pack so again I need to be careful to ensure my safety and that of my partners * I will be using glass beakers so I need to be careful, in the event of breakages I will in sure that all glass I cleared away and placed in the "broken glass" container. ...read more.

Conclusion

AVERAGE CHANGE IN MASS (grams) 5 0.0235g 10 0.0405g 15 0.0690g 20 0.0810g 25 0.104g Results taken from a secondary source The results I obtained from a secondary resource support my prediction that if the time increases the so does the amount of copper deposited on the cathode. It is also possible to say that if the time is doubled and therefore the charge is doubled then so is the amount of copper produced. This can be seen in the results: In 10 minutes 0.0405 grams of Copper is produced. In 20 minutes 0.0810 grams of Copper is produced. 0.0810 grams is exactly double 0.0405 grams. This proves the prediction that the longer the experiment lasts, the higher the charge and therefore, the higher the amount of Copper produced. The actual results produce an almost straight-line graph. Therefore, it has now been proved, through this experiment, that both of Faraday's Laws Of Electrolysis are correct. 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" Although my results were accurate I failed to record the correct information and I changed too many variables. Once I realised this there was only enough laboratory time left to obtain the results for 5 minutes and repeat this. These results were accurate; they proved my prediction and Faradays law. In order to improve this investigation I should continue to record results in the same way for varying times repeating each time at least once. The experimental results I obtain from a secondary source appeared to be very accurate and therefore they product of a successful experiment; however the following improvement are true for both experiments. The electrodes, which, even after a thorough cleaning were still fairly dirty and seemed to have irremovable substances from previous experiments still attached to them. If this experiment were to be repeated for a second time, to a greater degree of accuracy, it would be important to use a new pair of electrodes, which had never been used before. ...read more.

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