Link Statement:
I have noticed these two experiments are similar because their aims are alike as they depend on something to get a voltage. Also their methods are very similar.
Diagram:
Equipment:
-
200cm3 of Sulphuric acid- this is the electrolyte need for the electrochemical cell
- Beaker- to hold the sulphuric acid and the 2 metals placed in it
- 2 copper strips- one is needed
- 6 other metal strips- Tin, Iron, Lead, Aluminium, Zinc, Magnesium
- Voltmeter- to measure the amount of voltage between the two metals
- Holder with 2 crocodile clips- to hold the two metals
Method:
-
I will set up as shown in the diagram above with 200cm3 of sulphuric acid as the electrolyte
- I will use a holder with crocodile clips to hold both metals
- I will place the electrodes which are copper- copper into the acid and note the voltmeter reading immediately.
- I will then remove both electrodes quickly and wash and dry them.
- I will repeat steps 3-6 but for tin, lead, iron, aluminium, zinc and magnesium.
- I will then repeat steps 3-7 to get second set of results
Variable Table:
Fair Test:
I must keep the volume of the electrolyte (sulphuric acid) the same because different volumes have different amounts of particles. So I have to have the same volume of the electrolyte to have the same number of particles.
I must have the same type of electrolyte (sulphuric acid) as different electrolytes conduct different amounts of electricity. It has to be sulphuric to conduct the same amount of electricity.
I must wash and dry the metal electrodes because a displacement reaction can caused between the metal and salt solution so I to remove the electrolyte from the electrode.
The time in which the metal is in contact with the sulphuric acid as a displacement reaction can happen between the metal and salt solution. This is why I have to take the metals out immediately.
The room temperature must always be the same because it can speed up or slow down the reaction time in the electron flow.
The same person must do the same job as different people have different methods of measuring.
I must keep copper the same as this is the control metal because if I changed it my investigation would be completely wrong.
Safety:
To ensure that there is the optimum level of safety for me and others I must:
Wear safety goggles to ensure that no sulphuric acid comes in contact with anyone‘s skin
Make sure the sulphuric acid does not come in contact with anybody’s skin as it corrosive. If this happen, immediately wash it off with water.
Prediction:
I predict copper-magnesium will produce the most voltage as magnesium is the most reactive metal out of the 7 metals. This is because magnesium can lose its electrons more easily than the other metals as it is the only one in group 2.
An electrochemical cell converts chemical energy into electrical energy using a redox reaction. Depending on their chemical environment metals can be oxidised or reduced enabling apparatus to be set up to measure the potential electrical difference between two metals.
A redox reaction is like a displacement reaction. In a displacement reaction a metal is place in another metal’s salt solution. A stronger metal would displace a weaker one.
Because zinc is a more reactive metal than copper it prefers to form ions in solution, therefore the two reactions occurring are:
At the negative electrode: Oxidation
Zn(s) Zn2+ (aq) + 2e-
At the positive electrode: Reduction
Cu2+ (aq) 2e-Þ Cu(s)
The oxidation reaction gives out electrons and therefore occurs at the negative electrode (cathode) and the reduction occurs at the positive electrode (anode). These reactions are called half-cells or half-equations.
The overall reaction equation is therefore:
Zn(s) + Cu2+ (aq) Zn2+ (aq) + Cu(s)
Results Table:
Graph:
This is attached. It is bar chart and line graph to show
Analysis:
I have found out that copper-magnesium produces the most voltage and copper-copper produces the least. This is because magnesium is the most reactive metal out of all the seven metals, as it is the only one in group 2. Its looses its electrons more quickly and easily more than the transition metals because group 2 metals only have 2 electrons in their outer shell whereas transition metals have between 2-3 electrons in their outer shell
This is the order in which the voltage was produce:
Magnesium ➔ Group 2
Zinc
Aluminium
Tin Transition Metals
Iron
Lead
Copper
As shown in the graph magnesium is a more reactive metal than copper and it prefers to form ions in solution, therefore the two reactions occurring are:
At the negative electrode: Oxidation
Mg(s) Mg2+ (aq) + 2e-
At the positive electrode: Reduction
Cu2+ (aq) 2e- + Cu(s)
The oxidation reaction gives out electrons and therefore occurs at the negative electrode (cathode) and the reduction occurs at the positive electrode (anode). These reactions are called half-cells or half-equations.
The overall reaction equation is therefore:
Mg(s) + Cu2+ (aq) Mg2+ (aq) + Cu(s)
Evaluation:
My method was safe, clear and fair as I followed my method to every detail I had written. However I did receive two anomalous results which were aluminium and iron.
Aluminium was an anomalous result as it should have been below magnesium but in the experiment it came below zinc. As it had a layer of oxide on it so I had to take it off by using it sandpaper. Although I removed most of the oxide layer, I could not take it off. The oxide would have slowed down the flow of electrons and this why it came below zinc.
Iron was another anomalous result as it should have been underneath aluminium instead of tin. This result occurred because the crocodile clip on the holder did not hold the iron nail properly since it has an awkward shape.
To ensure that no anomalous results take place will make sure the crocodile clips will hold the metals correctly. I will use the same method and make sure that the oxide layer on the aluminium will be taken off.
This would be my new method:
-
I will set up as shown in the diagram above with 200cm3 of sulphuric acid as the electrolyte
- I will use a holder with crocodile clips to hold both metals
- I will make sure the crocodile clips
- I will place the electrodes which are copper- copper into the acid and note the voltmeter reading immediately.
- I will then remove both electrodes quickly and wash and dry them.
- I will repeat steps 3-6 but for tin, lead, iron, aluminium, zinc and magnesium.
- I will then repeat steps 3-7 to get second set of results
This will enable me get the results that I wanted
