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Electrolysis of Sodium Chloride - NaCl.

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Introduction

Electrolysis of Sodium Chloride - NaCl Plan Aim I aim to find out how the concentration of Sodium Chloride (NaCl) affects the current. Hypothesis Electrolysis is the decomposition of a substance or compound with the use of electricity. Electricity is the free-flow of electrons (or charged particles). An electrical current is only able to pass through a substance if the electrons (or charged particles) are able to move. Graphite's electrons are free to move, hence it is a conductor of electricity. Ions enable charges to move freely in solutions, and therefore also are conductors. There are two graphite electrodes; the negative electrode - the cathode, and the positive electrode - the anode. In this experiment the ions present are; NaCl = Na+, Cl� H2O = OH� and H+. Therefore; At the cathode; Na+, H+ The most reactive out of these remains in the solution ; 2 H+ +2e�= H2 (g) Here, we experience a gain of electrons, called a reduction At the anode; Cl�, OH� If a halogen is present, halogen gas given off - Cl2 Here, we experience a loss of electrons, called an oxidation Left in the solution; Na+, OH� Prediction I predict that as the concentration of Sodium Chloride (NaCl) ...read more.

Middle

Method > To obtain an average set of results and to make it a fair test, I will carry out 3 results per concentration of Sodium Chloride (NaCl). This will hopefully ensure I do not obtain any anomalous results > I will start by measuring 60ml of water in the measuring cylinder and pouring this into the beaker. > Next I will measure the desired concentration of Sodium Chloride, starting at 0.25g and increasing it by 0.25g for each test until it amounts to 2g, using the weighing boat and the weighing scales. I will need to measure the mass of the weighing boat first in order to get the mass of the NaCl whilst it is in the boat. > While doing this I will put the 2 electrodes in the water and ensure they are 2cm apart > I will then put in the desired concentration of NaCl and stir until it has dissolved. > I will then connect the circuit by attaching the ammeter to the connecting wires and the battery pack and then attaching the connecting wire to each electrode. I will then turn the battery pack on by the plug. > I will then check the reading on the ammeter and record the results. ...read more.

Conclusion

I think it was successful as I had scientific knowledge and a strong prediction that enabled me to support and gain the results I expected. However, I did obtain one anomalous result which has been highlighted both in the table and on the graph. I think I obtained this result because the electrodes were perhaps slightly further apart than desired, therefore the result was not near the line of best fit. Other than this I obtained a good set of results as I kept the experiment a fair test. The volume of water used was kept constant, at 60ml and 0.25g of NaCl was added for each test. I collected three results per mass of NaCl as this enabled me to get fair and reliable results. With the exception of one anomalous result I obtained, the distance between the electrodes was kept 2cm apart. This experimental method was suitable as it was quick and efficient, only lasting 3 lessons. If I were to do this experiment again, I would ensure I would keep the test entirely fair by ensuring I keep the electrodes the same distance apart at all times, and concentrate harder in order to do so. Also if I were to suggest an alternative mean of doing this experiment, I could collect the amount of gas produced in 1 minute. George Karsa Mr Van Mallearts Chemistry Coursework ...read more.

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