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Investigation to see how the voltage changes when we change the metals used in a cell

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Investigation to see how the voltage changes when we change the metals used in a cell Method During this investigation I performed two different experiments. Both experiments were to see how the voltage changed when using two different metals as electrolytes in a battery. When using sulphuric acid as the electrolyte I set up the experiment as shown in the diagram. The other experiment used a grapefruit (therefore citric acid) as the electrolyte. We set it up in the same way as we set up the experiment when using sulphuric acid, except we inserted the pieces of metal (the electrodes) into the grapefruit. The wires were attached to the pieces of metal using crocodile clips. We then held the metals in the electrolyte until the voltage reading on the voltmeter remained steady. I repeated the results once when using sulphuric acid, but did not have enough time to repeat the results when using citric acid. Results Sulphuric acid-1st set of results Metal 1 Mg Al Zn Sn Pb Cu Metal 2 Mg ------- Al 0.550 -------- Zn 0.130 0.330 --------- Sn 0.680 0.170 0.380 -------- Pb 0.870 0.170 0.640 0.240 -------- Cu 1.050 0.410 0.830 0.720 0.410 -------- Sulphuric acid-2nd set of results Metal 1 Mg Al Zn Sn Pb Cu ...read more.


If two metals that are very close in the reactivity series are used in the experiment, there will not be much difference as to which is more readily able to give up electrons. This would mean that the push of electrons would not be so strong, and therefore the voltage would not be so large. The electrons that flowed along the wire to the less reactive metal join with ions in the solution and form additional metal onto the surface of that metal. The more reactive metal is gradually eaten away (oxidised as it is losing electrons) and the less reactive metal is being reduced (it is gaining electrons). This is why the voltage is higher when the metals used are further apart in the reactivity series. If one of the metals used is very reactive because of its electronic configuration it is much more able to lose electrons and therefore the flow of electrons is faster and a higher voltage is produced. When the other metal is very low, and so they are very far apart in the reactivity series, it is much more ready to gain electrons and so this also helps the electron flow to be increased and the voltage therefore also to be increased. ...read more.


This could have decreased the speed of the flow of electrons and reduced the voltage. The opposite effect would be produced if the temperature was decreased. If I did the experiment again, I would have used the standard conditions for the experiment. The 'Heinemann Advanced Science Chemistry' textbook states that the conditions are as follows; 1) All measurements are made at 25?C. 2) All solutions are to have unit activity (effectively 1.00 mol dm-3). 3) All measurements are made at 105 Pa pressure. The diagram above shows how I would set up the experiment when using Zinc and Copper. Instead of having the pieces of metal (the electrodes) in one beaker I would prevent the solutions in each beaker from mixing by separating the metals, one in each beaker. The salt bridge which consists of agar jelly with added potassium chloride (potassium nitrate can be used) allows charge to pass through it to complete the circuit, but limits diffusion of the solution. I would also have used a high resistance voltmeter, which would have given more accurate results. If I was to repeat this investigation I would also have made more repetitions of my results so I could have come to a better conclusion as to what the electrode potentials were for this experiment. ?? ?? ?? ?? Eleanor Piercy 10SJ ...read more.

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