Ib Redox Planning Task

Redox вЂ" Planning Task

How Does the Voltage Produced by an Electrochemical Cell Change for Different Volumes of the Electrolytes?

Introduction: A simple voltaic cell is made of two half cells. One of these is simply a metal in contact with an aqueous solution of its own ion. What connects the half-cells are the salt bridge and an external wire, which allows free movement of ions. The purpose of the salt bridge is to maintain electrical neutrality for the overall cell. Electrons are enabled to be transferred during the redox reaction and thus, producing energy in the form of electricity. In this experiment, the voltaic cell will be made of a magnesium half-cell and a copper half-cell, using MgSO4(aq) and CuSO4(aq) as their respective electrolytes. The Standard Electric Potentials for Magnesium half-cell is -1.18V and for Copper half-cell is +0.34. The importance of these values will be mentioned below.

Aim: To investigate the changes in the voltage produced by changing the volume of the electrolyte.

Hypothesis: In this experiment, it will be expected to be seen more voltage produced as a greater volume of electrolytes are used. Initially, since magnesium is higher in the reactivity series, the electrons will flow from the magnesium half-cell to the copper half-cell through the external wire and the voltmeter will measure the potential difference between the metals. At the negative electrode (anode), the metal will slowly dissolve as these electrons are removed (oxidation). At the less negative electrode (cathode), the incoming electrons react with the metal ions to form a layer of the metal (reduction). This process will continuously happen until the magnesium or copper sulphate is all consumed. Therefore, if there is a greater amount of electrolyte, this process will be more lasting; eventually producing more voltage.

The salt bridge will maintain the cell neutrality since, at the anode, positive ions are produced and at the cathode they are being consumed. As a result, it allows positive ions to move from the anode to the cathode and negative ions from the negative ions to move from the cathode to the anode.

Our results, however, may differ from our initial predictions. One possible problem that may be encountered is the systematic errors of the apparatus. One systematic error could arise from the voltmeter, but this should not present such a problem since it will already be taken into consideration in our data collection. Another possible systematic error (which may also be seen as a random error) is the length of the electrode used. Initially, there is the error of using a ruler to measure out equal lengths of electrode. However, the thickness of the metals may also vary, causing there to be different amounts of electrode and opening room for further inaccuracies in our data collection. Since it is practically impossible to measure exactly equal strips for the electrode, we shall measure the mass of each electrode and try to provide practically equal masses. Still, there will be the error the balance used, but this can be more easily taken into account, since it is an exact value.

Variables

The key variables of the experiment

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