Find out how magnesium ribbon reacts with various chlorides.
Compare the reactivity of the Transition Metals with the elements in Group 2.
This investigation aims to find out how magnesium ribbon reacts with various chlorides including zinc chloride, iron chloride, copper chloride, nickel chloride and cobalt chloride, as compared to the reactivity of the elements in group two. All the elements that combine with the chloride ions to form the compounds are transition metals.
Reactivity series.
The reactivity series is a list of metals in order of reactivity with the most reactive metal at the top of the list and steadily decreasing reactivity down the list. The list is as follows:
Potassium K
Sodium Na
Calcium Ca
Magnesium Mg
Aluminium Al
Zinc Zn
Iron Fe
Lead Pb
Copper Cu
Mercury Hg
Silver Ag
Platinum Pt
Note: this list could be shorter or longer depending upon the number of metals you wish to consider.
As I have mentioned above, all the elements that have been combined with the chloride ions to form the chloride compounds are transition metals. This means that the reactions that will take place may not be in any obvious order e.g. in order of reactivity, thus I will have to investigate and find out in what order they will react.
Transition Metals.
Transition metals have the following properties in common: -
> The metals have higher melting points, boiling points and densities than group 1 metals
> The metals are usually strong and shiny.
> They are good conductors of heat and electricity (just like other metals).
> Some of these metals have strong magnetic properties.
> Transition metals often form more than one positive ion.
> Transition metal compounds are often coloured e.g. copper chloride is blue.
> Transition metals and transition metal compounds are often good catalysts e.g. nickel is the catalyst used to turn oils into fats for making margarine, and iron is the catalyst used in the Haber process for making ammonia.
Arrangement of particles in an atom
The protons and neutrons are tightly packed in the nucleus of an atom. The electrons move rapidly around the nucleus in distinct energy levels. Each energy level is capable of accommodating only a certain number of electrons.
The first energy level can hold only two electrons. This energy level is filled first.
The second energy level can hold only eight electrons. This energy level is filled after the first energy level and before the third energy level.
The third energy level can hold a maximum of 18 electrons. However, when eight electrons are in the third energy level there is a degree of stability and the next two electrons added go into the fourth energy level. Then extra electrons enter the third energy level until it contains the maximum of 18 electrons.
There are further energy levels, each containing a larger number of electrons than the preceding energy level. You will find that properties of elements and the position in the periodic table are related to electronic structure. The electronic structure 2,8,1 denotes 2 electrons in the first energy level, 8 in the second, and 1 in the third. This is sometimes called the electronic configuration of an atom.
The electronic structure of the atom.
You can imagine a model of an atom with electrons orbiting in shells around the nucleus. The electrons in each successive shell have an orbit further away from the nucleus. A more advanced model of electron structure is used in which each shell is made up of sub-shells.
Sub-shells.
There are different types of sub shell: s, p, d and f. each type of sub-shell can hold a different number of electrons.
Sub-shell
Electrons
s
2
p
6
d
0
f
4
The table below shows the shells and sub-shells, and their configuration.
Shell
Sub-shell
Total number of electrons
st shell
s
2 =2
2nd shell
2s 2p
2 + 6 =8
3rd shell
3s 3p 3d
2 + 6 + 10 =18
4th shell
4s 4p 4d 4f
2 + 6 + 10 + 14 =32
> Each successive shell contains a new type of sub-shell.
> The 1st shell contains 1 sub-shell, the second sub-shell contains 2 sub-shells, and so on.
Orbitals.
How do the electrons fit into the sub-shells? Mathematicians have worked out that
electrons occupy negative charge clouds called orbitals and these make up each sub-shell.
> An orbital can hold up to two electrons.
> Each type of sub-shell has different orbitals: s, p, d and f.
The table below shows how electrons fill the orbitals in each sub-shell.
Sub-shell
Orbitals
Electrons
s
x 2 = 2
p
3
3 x 2 = 6
d
5
5 x 2 = 10
f
7
7 x 2 = 14
s-orbitals
> An s-orbital has a spherical shape.
p-orbitals
> A p-orbital has a three dimensional dumb-bell shape.
> There are three p-orbitals, px, py and pz, at right angles to on another.
d-orbitals and f-orbitals.
The structures of d and f-orbitals are more complex.
> There are five d-orbitals
> There are seven f-orbitals.
How do two electrons fit into an orbital?
Electrons are negatively charged so they repel one another. An electron also has a property called spin. The two electros in an orbital have opposite spins helping to counteract the natural repulsion between their negative charges. Within an orbital, the electrons must have opposite spins.
Filling the sub-shells
Sub-shells have different energy levels. The diagram below shows the relative energies for the sub-shells in the first four shells.
> Shells and sub-shells are occupied in energy-level order.
> Within a shell, the sub-shell energies are in the order: s, p, d and f.
> Electrons occupy orbitals singly to prevent any repulsion caused by pairing.
The 2s orbital is occupied before the 2p orbitals because it is at a lower energy. Note that the 4s sub-shell is at a lower energy than the 3d sub-shell and therefore the 4s sub-shell fills before the 3d sub-shell.
Electronic configuration.
The electronic configuration of an atom is a shorthand method showing how electrons occupy sub-shells.
Examples:
Boron: atomic number 5
Electronic configuration: 1s22s22p1
The electronic configurations can get more complicated depending on the element.
e.g.
Potassium: atomic number 19
Electronic configuration: 1s22s22p63s23p64s1
Simplifying electronic configurations.
The similar electronic configurations within a group of the periodic table can be emphasised with a simpler representation in terms of the previous noble gas.
e.g.
The last noble gas before potassium is argon. Argon's electronic configuration is 1s22s22p63s23p6 so therefore the electronic structure of potassium can be shortened to [Ar] 4s1.
Argon is the last noble gas before all of the transition metals so they will all be shortened to have [Ar] before the rest of their electronic ...
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e.g.
Potassium: atomic number 19
Electronic configuration: 1s22s22p63s23p64s1
Simplifying electronic configurations.
The similar electronic configurations within a group of the periodic table can be emphasised with a simpler representation in terms of the previous noble gas.
e.g.
The last noble gas before potassium is argon. Argon's electronic configuration is 1s22s22p63s23p6 so therefore the electronic structure of potassium can be shortened to [Ar] 4s1.
Argon is the last noble gas before all of the transition metals so they will all be shortened to have [Ar] before the rest of their electronic configuration.
Nickel - [Ar] 3d84s2
Cobalt - [Ar] 3d74s2
Copper - [Ar] 3d104s1
Zinc - [Ar] 3d104s2
Iron - [Ar] 3d64s2
Factors affecting ionisation energy.
Ionisation energy measures the ease with which electrons are lost in the formation of positive ions. An ion has as many ionisation energies as there are electrons.
Electrons are held in their shells by attraction from the nucleus. The first electron lost will be from the highest occupied energy level. This electron experiences least attraction from the nucleus.
Three factors affecting the size of this attraction are shown below.
Atomic radius
The greater the distance between the nucleus and the outer electrons, the less the attractive force. Attraction falls rapidly with increasing distance and so this factor is very important and has a big effect.
Nuclear charge
The greater the number of protons in the nucleus the greater the attractive force. This is caused by a greater positive charge attracting the negative electrons.
Electron shielding or 'screening'
The outer shell electrons are repelled by any inner between the electrons and the nucleus.
This repelling effect, called electron shielding or screening, reduces the overall attractive force experienced by the outer electrons.
General trend.
> There is a general rise in the first ionisation energy across a period.
> The nuclear charge increases giving a greater attraction.
> There is little variation in atomic radius.
> Electrons are added to the same shell, that is the same order of distance from the nucleus.
> All elements in the period experience the same degree of electron shielding from inner shells.
> There is only one inner shell for all elements in period two.
> Across a period, the increased nuclear charge is the most important factor and the greater attractive force leads to an increased first ionisation energy.
Electron arrangement and reactivity in a group.
The number of electrons in the outer energy level controls the chemical properties of an element. As elements in the same group have similar properties, we should expect some similarity in their electronic arrangement.
The table below shows the arrangement of electrons in the alkali metal family (group 1)
Element
Atomic number
Arrangement of electrons
Lithium
3
2,1
Sodium
1
2,8,1
Potassium
9
2,8,8,1
Rubidium
37
2,8,18,8,1
Caesium
55
2,8,18,18,8,1
Note that in each case, the outer energy level contains just one electron. When an element reacts it attempts to obtain a full outer energy level. Group 1 elements will lose one electron when they react and form a positive ion.
We can explain the order of reactivity within the group. The electrons are held in position by the electrostatic attraction of the positive nucleus. This means that the closer the electron is to the nucleus, the harder it will be to remove it.
As we go down the group, the outer electron gets further away from the nucleus and so becomes easier to take away. This means as we go down the group, the reactivity should increase.
The table below shows the arrangement of electrons in the alkaline earth metal family (group 2).
Element
Atomic number
Arrangement of electrons
Beryllium
4
2,2
Magnesium
2
2,8,2
Calcium
20
2,8,8,2
Strontium
38
2,8,18,8,2
Barium
56
2,8,188,18,8,2
As the atoms all have 2 electrons in their outer energy level, they will lose two electrons to form positive ions. More energy will be required to remove two electrons and so they will not be as reactive as the group 1 metals. As with group 1, the reactivity will increase down the group.
The table below shows the arrangement of electrons in the halogen family (group 7).
Element
Atomic number
Arrangement of electrons
Fluorine
9
2,7
Chlorine
7
2,8,7
Bromine
35
2,8,18,7
Iodine
53
2,8,18,18,7
Note that each member of the group has seven electrons in the outer energy level. This is just one electron short of the full energy level. When halogen elements react, they gain an electro to complete that outer energy level forming a negative ion.
As an electron is being gained the most reactive member of the family will be the one where the extra electron is closest to the nucleus i.e. fluorine. The reactivity decreases down the group.
Trends within a period.
From left to right in any period the atoms gradually decrease in size. This surprises many people because, going from left to right, each element has one more electron than the previous element. However, this electron goes into the same energy level and the extra positive charge on the nucleus, caused by the extra proton, increases the attraction on the electrons and makes the atom slightly smaller.
Magnesium
Name: Magnesium
Symbol: Mg
Atomic Number: 12
Atomic Mass: 24
Atomic Structure
Iron
Name: Iron
Symbol: Fe
Atomic Number: 26
Atomic Mass: 56
Atomic Structure
Cobalt
Name: Cobalt
Symbol: Co
Atomic Number: 27
Atomic Mass: 59
Nickel
Name: Nickel
Symbol: Ni
Atomic Number: 28
Atomic Mass: 59
Atomic Structure
Copper
Name: Copper
Symbol: Cu
Atomic Number: 29
Atomic Mass: 64
Atomic Structure
Zinc
Name: Zinc
Symbol: Zn
Atomic Number: 30
Atomic Mass: 65
Atomic Structure
I have carried out some preliminary tests before implementing the main experiment so that I should be able to estimate the time period for which I will leave the experiment running. This should also help me with my predictions and hypothesis. I estimated that I would need an experiment time of one minute for each chloride. However, when I tested a few chlorides, the reactions were much slower than previously thought, so I extended the time to two minutes for each chloride.
In my background information I have stated that as you go down group one and two of the periodic table the reactivity of the elements increases. This is because every time you go down an element another outer shell has been added. As a result the shielding effect increases, as the electrons in the outer shell get further away from the nucleus therefore experiencing less electrostatic attraction. This then makes it easier for the atom to loose these outer electrons.
However, when you go across a period more and more electrons are added to the same outer shell, but at the same time more protons are being added to the nucleus. Because there are no outer shells being added, the electrons don't experience less of an electrostatic attraction but instead they experience more of an attraction, as there is a greater positive force at the nucleus due to the addition of the protons. As a result the greater positive force and the greater negative force are strongly attracted towards each other causing the atom to become slightly smaller.
Therefore, I predict that as you go across a period, the reactivity should decrease due to the above reason. So, as the relative atomic mass increases, the amount of solution it displaces should decrease. The order of reactivity should thus go as follows:
Iron chloride
Cobalt chloride
Nickel chloride
Copper chloride
Zinc chloride
A similar previous experiment that involved reacting elements in their solution form with other elements in their solid form on a tile strengthened my hypothesis. In this previous experiment, magnesium, zinc and lead were reacted with magnesium chloride, zinc chloride and lead chloride on a tile. The results were as follows:
Magnesium reacted with zinc chloride and lead chloride because they are more reactive than magnesium.
Zinc only reacted with lead chloride because it is the only element more reactive than lead.
Lead didn't react with any of the chlorides as none of them were more reactive than lead.
This indicates that metals react in a series and will only react well if the solution they are placed in is more reactive than the metal itself.
Below is a list of the apparatus and equipment that I used to carry out the experiment:-
> Magnesium ribbon (approximately 0.01g)
> Beakers
> Test tubes
> Test tube racks - to put the test tubes in
> Ruler - to measure how much displacement will occur
> Gloves - to prevent any harm to my hands
> Goggles - to prevent any harm to my eyes
> Cobalt chloride (0.25M)
> Zinc chloride (0.25M)
> Nickel chloride (0.25M)
> Iron chloride (0.25M)
> Copper chloride (0.25M)
> Balance - to weigh the magnesium upon
> Lighter and splint - to test the gas produced
> Water - to clean everything with
> Stationery - to record the results with.
The following diagram shows how the apparatus was set up:-
A fair experiment is one in which there is only one independent variable which is manipulated to observe its effect on the dependant variable. Thus, fair testing plays an important role in this experiment as it would in any other. A fair test provides accurate and valid results such that I would be able to draw concrete conclusions from.
All the measurements carried out will have to be as precise and accurate as possible so as to avoid attaining anomalous results:
> A clean and empty flask was used to put the chloride compounds in.
> All the test tubes used were clean and contained no residue. I also checked that none of the test tubes were broken or cracked, as this will have an effect on the results obtained.
> I made sure that all of the test tubes that I used were of equal size so that when I measured how much of the chloride solution had been displaced, I got the correct volumes.
> The amount of chloride solution displaced was measured to the nearest millimetre using a ruler
> A sensitive balance was used to weigh the magnesium strips separately to the nearest 2 decimal places. I also made sure there was no dirt or water on the balance before use, because even the smallest things could affect the results.
> I made sure that the magnesium strip was swiftly removed as soon as the time was up so that whilst measuring how much solution had been displaced, the magnesium strip wasn't still reacting.
> It was important to make sure that all the magnesium strips were of the same size and mass using an accurate ruler (nearest mm) and sensitive balance (2 decimal places). This is because if there were more magnesium in one of the experiments it would react faster and cause anomalous results, as there is a bigger surface area that can be reacted.
> All of the experiments were carried out for equal amounts of time so that my results were as accurate as possible and can be compared (except for the iron chloride which displaced all of the solution before the provided time had elapsed).
> I made sure that the test tubes were put into the beaker in a way such that no air bubbles were let in as this would lead to anomalous results.
> It was important that all the test tubes had equal amounts of solution in them (filled to the brim) because a different volume of one solution in a test tube would affect the pattern of results later on.
> I repeated the experiment three times to ensure that I have a good average of results from which to draw a conclusion. Replication ensures validity of the results obtained.
> I made sure that I always wore goggles and gloves during the carrying out of the experimentation and that no one close by was in any sort of danger for safety reasons.
> Each time I carried out the experiment I made sure that I used the same equipment and processes so as to ensure fluency.
> I made sure that the same person carried out all of the experimentation to achieve accuracy and precision during the carrying out of the experiments.
Safety is a very important aspect in every experiment and needs to be taken into consideration even if the experiment seems relatively harmless, such as this one.
I will be careful not to swallow any of the solution or let any of it enter my eyes or body as it could cause severe damage. To prevent this from happening I will use gloves and goggles.
Some of the reactions might be quite violent and rigorous and so I will have to make sure that there is no one close to me when I am carrying out the experiment, as I do not want any of the solution splashing on anyone because of the hazards.
When testing the gas that has been produced after the experiment, we should be careful and wear gloves and goggles, as we are not sure of the gas that has been produced and how it will react with a flame (e.g. small explosion).
Other than this, I do not think that they are any other safety matters to be cautious of.
The only independent variable in this experiment was the chloride solution being used.
The dependant variable in this experiment was the amount of chloride solution that is displaced. This is because it depends on the chloride solution being used.
The constants during this experiment will be the volume of the solution, size of magnesium strip, duration of experiment, size of the test tubes (except for one), temperature and other environmental conditions. I will also make sure that I use the same equipment all the time so as to ensure that the measurements are as comparable as possible.
. Wear the gloves and goggles.
2. Gather the required apparatus and set it up as shown in the diagram above.
3. Pour enough of one of the solutions into a clean beaker.
4. Take a clean and dry test tube and fill it to the brim with the required solution.
5. Place a magnesium strip into the test tube and quickly place my thumb over it
6. Turn the test tube upside down and place it into the beaker, partially submerged in the solution.
7. Turn on the timer and wait for two minutes elapse.
8. After two minutes have elapsed, swiftly remove magnesium strip and place thumb on the end of the test tube.
9. Remove the test tube and measure how much of the solution had been displaced using an accurate ruler (nearest mm).
0. Record the results on the results table.
1. Test the gas given off using a lighted splint.
2. Repeat same method for all chloride solutions three times.
Note: all of the magnesium strips where weighed and measured beforehand using a sensitive balance (2 decimal places.)
Transition metal
2
3
Average
Volume displaced (cm3)
% Decrease
Nickel
0.5
0.5
0.4
0.47
0.45
6.27
Cobalt
.1
.2
.1
.13
.07
5.06
Copper
3.7
3.8
2.9
3.47
3.30
46.27
Zinc
4.5
3.4
3.8
3.90
3.71
52.00
Iron
5.9
6.0
6.5
6.13
9.44
49.04
Note: Test Tube size (small):-
Diameter - 1.1 cm
Height - 7.5 cm
Mathematical formula for volume: ? x (radius)2 x height
% decrease = displaced/original x 100
Nickel
Volume: ? x 0.55 x 0.55 x 0.47 = 0.45cm3
% decrease: 0.47/7.5 x 100 = 6.27%
Cobalt
Volume: ? x 0.55 x 0.55 x 1.13 = 1.07cm3
% decrease: 1.13/7.5 x 100 = 15.06%
Copper
Volume: ? x 0.55 x 0.55 x 3.47 = 3.30cm3
% decrease: 3.47/7.5 x 100 = 46.27%
Zinc
Volume: ? x 0.55 x 0.55 x 3.90 = 3.71cm3
% decrease: 3.9/7.5 x 100 = 52.0%
Iron
This was a very reactive reaction so a larger test tube was used. These were the dimensions:
Diameter -1.4 cm
Height -12.5 cm
Volume: ? x 0.70 x 0.70 x 6.13 = 9.44cm3
% decrease (larger test tube): 6.13/12.5 x 100 = 49.04%
As I have mentioned in my hypothesis, I think that as you go across a period, the reactivity should decrease, therefore I am going to plot my graph of relative atomic mass against volume to prove whether my hypothesis is correct or incorrect.
Transition metal
Relative atomic mass
Volume displaced (cm3)
Nickel
59
0.45
Cobalt
59
.07
Copper
64
3.30
Zinc
65
3.71
Iron
56
9.44
As noted above, each of the experiments was carried out three times, after which an average was calculated and graphed so as to allow for comparison and its analysis. It is obvious from the graph that there is no correlation thus proving my hypothesis wrong. However, this doesn't make the graph and table totally useless as useful information can still be extracted. A line of best fit was unable to be established because of the vast difference in where the points were dispersed.
The table shows that nickel and cobalt have the same relative atomic mass however, the table also shows that cobalt produced a higher volume of hydrogen as compared to nickel.
According to my hypothesis iron should have reacted the fastest despite being so low down in the reactivity series and this is shown in the graph and table. Had iron been lower than nickel it would have been possible to say that there was a correlation. However, iron reacted so much faster than all of the other metals that it could not have been an anomaly, although it might be marginally wrong.
Zinc on the other hand, was supposed to be the least reactive according to my hypothesis but it turned out to be the second most reactive. Zinc is quite high up in the reactivity series and so my result could be due to this. This therefore indicates the invalidity of the theory I put forward in my hypothesis.
If I were to join up the all the points in my graph it would not be possible to find any pattern such as a smooth curve a straight line or other trends. This may be due to the fact that there are anomalies but may also be as a result of testing a very small proportion of the transition metal group, thus not allowing for enough data to generalize from and compare ensuring validity.
It must also be noted from my graph that there are very few points making it difficult to make any concrete deductions or conclusions. It is possible to say that there is no correlation because there are other factors that may be affecting the results. To verify this I will compare the volume of gas produced with the atomic number. By comparing these variables, I will be able to see whether the number of protons plays a part in the reactivity series of transitional metals.
Again, no line of best fit can be drawn because the points are dispersed and follow no real pattern. This shows that the proton number alone doesn't affect the reactivity of the transition metals either.
Although a few minor experimental errors and anomalies have been noted, it is obvious that the data gathered didn't prove to be valid enough to draw concrete conclusions from regarding the reactivity of the transition metals.
Despite being quite low on the reactivity series, iron chloride produced the most gas i.e. displaced the most amount of solution in the given time. Although I cannot be sure why this happened a suggestion can be made. Magnesium is a group two element, which means that it will willingly give away two electrons. Iron's electronic configuration is [Ar] 3d64s2 . This shows that it needs two electrons to fill its 3d orbital and bring it into a stable position suggesting why it reacted so well.
It was also noted that coppers electronic configuration is [Ar] 3d104s1. This is unusual because the 4s sub shell usually fills completely with two electrons before the 3d orbital is filled. This is done because it puts copper in a more stable form. This may be a reason leading to why copper reacted the way it did and possibly affect my results.
Through my research I found out that transition metals have varying oxidation numbers. Oxidation is the tendency of an atom to loose electrons. Group 1 elements have an oxidation number of 1 meaning that in a reaction they will lose one electron. All of the groups have set oxidation numbers meaning that in any reaction they will only lose a particular number of electrons. But for the transition metals it is different because they have varying oxidation numbers. This is probably the most likely reason why my results showed no correlation.
Also, other factors such as the spin-pairs of electrons, half-shell and half-fields of the atoms weren't taken into account during the experiment as well as when accounting for the data gathered.
Finally, although various faults have been noted with the experimental procedure (as will be accounted for in the evaluation), the overall planning of the experiment was detailed, cons ice and allowed for the collection of the relevant data gathered.
Various experimental errors and some minor anomalies were noted in the data gathered and through its analysis. It is necessary to note these so as to understand their effect in the data gathered.
One experimental error could be human error or inaccuracy in precision when carrying out any one of the tasks. Human inaccuracy and error will always be present and we are unable to eliminate it as long as humans play a part in carrying out experiments.
Modifications for further research would include more time allocation so as to allow the researcher not to rush but to pace themselves out so as to complete the various experimental tasks and redo the experiment where required or to allow for replication.
Another point is that a larger variety of solutions (transition metals) could have been used, as this would allow me to draw concrete conclusions and it would also eliminate the problem of identifying which points are anomalies and which ones aren't when they are very few points. As well as this, we could have tested a wide range of metals other than magnesium on the five chloride solutions and see how they would react. This would make the test fairer as different metals react differently to different solutions.
To continue, other sources of error that need to be taken into consideration include the method that we used. It was quite difficult to handle the test tube when trying to partially submerge it in the solution as well as when removing. The method could be modified such that it makes it easier to handle the test tube making my carrying out of the experiment that much more accurate.
Using a measuring cylinder instead of the test tube could develop the method. It would make it lot easier to measure the gas produced rather than using a rather shaky ruler. Another idea would have been to use a gas syringe. This would make the measuring of the gas produced a lot easier and a lot more accurate.
One problem with the method led us to redo many of the experiments. During many of the reactions the magnesium strip got stuck to the side, which stopped the reaction for a few seconds. This problem was persistent especially with the reaction of the iron chloride because it reacted so quickly. This was the reason why many of our results aren't as precise as we wished them to be. It was also very time consuming to have to redo the experiments. I have yet to come up with a suggestion that could help overcome this problem.
Because of the size of the magnesium strips it was very difficult to make sure they were all exactly the same size although I am sure that they weren't. This would affect our results because when there is even a little bit more magnesium in any one of the experiments the reaction is likely to be faster because there is a larger surface area of the magnesium being reacted.
Another problem associated with the magnesium strips was when they came out from the test tubes. We were forced to keep the test tubes slightly elevated and this allowed the magnesium to slip out. Also not all of the gas was collected in the test tubes. Undoubtedly some of the gas was lost outside the test tube. Ag gas syringe would have ensured that near enough most of the gas was collected.
Precision and accuracy was lost when the given time had elapsed and we struggled to remove the magnesium strip in time. The extra few seconds that it was reacting could have been crucial if we are considering the speed at which the iron was reacting. Once again this problem could have been counteracted by the use of a gas syringe. The moment the time elapses the rubber bung can either be undone or the gas pipe blocked. Thus resulting in much more concrete results.
We faced a problem with contamination of the solutions as we were forced to use the same solution over and over again. The contamination is likely to have affected our results because they were remnants from previous experiments in them. All of the solutions were meant to be of the same strength i.e. 0.25M but we are not 100% sure of this and so this could have affected our results.
Finally, having done this experiment on the reactivity of transition metals, a further area of interest would be in the variety of the colours produced when transition metals react as they are noted to form coloured oxides.
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Chemistry revision guides by coordination publications
Letts GCSE Chemistry study guide.
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Nuffield Advanced Chemistry by Longman.
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