Analyzing Reactivity: Insights from Metal Activity Series and Reaction Observations

When predicting the results of the reactions in my hypothesis, I relied heavily on the activity series of metals chart. I predicted these results based on which metal was higher or lower on the activity series chart; those metals that were higher were more reactive, and therefore, should have been able to displace those metals that were lower on the chart.

Contrarily, those metals that were lower on the chart were less reactive, and therefore, should not have been able to displace those metals that were higher on the chart. As predicted, a single displacement reaction did occur in test numbers 1, 3, 4 , and 6; the metals put into the solutions were higher on the activity series chart, and were therefore able to displace the metals from the solution.

However, a single displacement reaction did not occur for test number 5; there were no changes present in the test tube after 24 hours, and therefore, my prediction was wrong. According to the activity series chart of metals, a single displacement reaction should have occured, but it did not; this is because I did not consider other significant factors that could have impacted my results.

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For instance, temperature, concentration, surface area, the types of elements involved in the reaction and their properties, could significantly impact the end result. These factors should have been taken into account before making the prediction.

Furthermore, as predicted, a single displacement reaction did not occur in test number 2; according to the activity series chart, the metal put into the solution was less reactive and was therefore unable to displace the metal from the solution. However, another type of reaction did occur; there were changes present in the test tube after 24 hours. A new bright orange powder appeared at the bottom of the test tube; this indicated a chemical change, and therefore, a reaction did occur. This could not have been a single displacement reaction; if a single displacement reaction did occur for test number 5, none of the products produced would be a bright orange coloured solid. Thus, my prediction was not completely correct; although a single displacement reaction did not occur, another reaction must have occured. As mentioned above, this simply indicates that there must be other factors that could have impacted the final results of this reaction; they should have been taken into account.

There were a few inconsistencies within this lab; specifically in test numbers 2 and 5. In test number 2, a single displacement reaction did not take place, but a bright orange solid was produced; the formation of this solid was a result of the process known as corrosion. Corrosion is when “a refined metal is naturally converted to a more stable form such as its oxide, hydroxide or sulphide state this leads to deterioration of the material.” (What is Corrosion, n.d). Metal corrodes when it reacts with another substance such as oxygen, hydrogen, an electrical current or even dirt and bacteria. In this case, iron is the corroding metal; the most common type of iron corrosion occurs when it is exposed to oxygen and the presence of water, which creates an iron oxide commonly called rust. The orange solid formed at the bottom of the test tube during this reaction is rust, or iron oxide, which can also be orange in colour. As mentioned above, both oxygen and water are required for rust to form; therefore, if an iron nail is immersed in deoxygenated water, it will not rust (LibreTexts, 2019). However, in test number 2, the iron nail was placed in a solution of magnesium nitrate; this solution consists of the compound magnesium nitrate as the solute and water as the solvent.

The water was not deoxygenated; thus, the rust was likely to form. This formation of rust involves two simple steps. The first step in the rusting process involves the dissolution or the ‘dissolving’ of solid iron into the solution; it can be written as Fe(s) → Fe2+(aq) + 2e-. The electrons produced by this reaction join with hydrogen ions within the water as well as with the dissolved oxygen to produce water: 4e- + 4H+(aq)+ O2(aq) → 2H2O(l). Thus, these two reactions produce water and iron (II) ions, but not rust; for rust to form, another reaction has to occur. Overall, these reactions leave a significant amount of hydroxide (OH-) ions in the water. The iron (II) ions react with these hydroxide ions to form green rust: Fe2+(aq) + 2OH-(aq) → Fe(OH)2(s). The iron (II) ions also join with hydrogen and oxygen in the water to produce iron (III) ions: 4Fe2+(aq) + 4H+(aq) + O2(aq) → 4Fe3+(aq) + 2H2O(l). These iron ions join with the extra hydroxide ions to form iron (III) hydroxide: Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s). This compound dehydrates - a dehydration reaction is a conversion that involves the loss of water from the reacting molecule or ion - to become Fe2O3(s).H2O(l), which is the chemical formula for rust. The balanced equation can be written as: 4Fe(s) + 3O2(g) + 6H2O(l) → 4Fe(OH)3(s). In addition to that, test number 5 was also an anomaly; according to the activity series chart, a single displacement reaction should have taken place, but it did not. One possible reason for this could be that the rate of reaction was very slow; it is possible that the reaction would have occured after 24 hours. The rate of reaction varies for each reaction depending on the activation energy of the particular reaction, the temperature at which the reaction takes place, and how often the reactants actually collide; certain reactions can take place at a slow rate, and therefore they can take days, months or even years to complete (fun science, n.d.).

Because tin and lead are very close to each other on the activity series chart, the activation of energy in this reaction could have taken longer than usual; normally, the greater the difference in reactivity between two metals in a displacement reaction, the greater the amount of energy released (bbc, n.d.). Thus, it is very possible that a reaction could have occured after 24 hours. Furthermore, the reduction potential of tin is -0.14 and the reduction potential of lead is -0.13; reduction potential (also known as redox potential, oxidation/reduction potential) measures the tendency of particles to gain electrons and therefore be “reduced”. Reduction potential is measured in volts (V) or millivolts (mV). Elements with a higher (more positive) reduction potential tend to gain electrons from the other substances and elements with a lower (more negative) reduction potential tend to lose electrons to the other substances (lumen, n.d.).

Because tin is more negative, it would lose its electrons and become an ion while joining the solution; the lead ions (from the solution/compound) would gain electrons and become neutral. However, their reduction potentials are very close together; this also means that this process will take longer than usual. Thus, the rate of reaction for test number 5 seems to very slow; a reaction was likely to occur after 24 hours. Moreover, test number 1 was slightly inconsistent as well; test number 1 had a higher rate of reaction compared to the other tests. The rate of a reaction is the speed at which a chemical reaction occurs. If a reaction has a low rate, that means the particles combine at a slower speed than a reaction with a high rate (Chem4Kids, 2018). The rate of reaction can be observed by watching the disappearance of a reactant or the appearance of a product over time (lumen, n.d.). In test number 1, silver, which was a product of the reaction, was visible in only a few minutes; thus, test number 1 had a high rate of reaction. However, test numbers 2, 3, 4, and 6 had a slower rate of reaction; their products were only visible after 24 hours.

This proves that test number 1 had a higher rate of reaction compared to the other tests. Although copper and silver are not located far apart on the activity series of metals chart, silver is located very close to the bottom on the chart; it is highly unreactive and it can therefore be displaced easily. The other tests involved metals higher up on the activity series chart, thus, those metals were harder to displace; for this reason, those tests had a lower rate of reaction in comparison to test number 1. Also, silver has a reduction potential of 0.8 whilst copper has a reduction potential of 0.34. Because copper has a lower reduction potential, it will lose its electrons and become an ion and join the solution whilst silver has a higher reduction potential; the silver ion will gain electrons and become neutral. The difference in the reduction potential in this test was greater than in the other tests; thus, the rate of reaction was faster in test number 1 than in the other tests.

Numerous factors, such as the concentration, the environment, the types of elements involved in the reaction and their properties, could have significantly impacted the result of these tests. These factors should have been taken into account before making the prediction. For instance, the amount of material used during each test could not have been accurate; the measurement of each solution was not very precise. It is possible that the amount of solution used for each test was different, which can result in inaccurate findings. This is because the concentration used during a reaction can significantly impact the overall result; when the concentration of all the reactants increases, more particles interact to form new compounds, and the rate of reaction increases. Contrarily, when the concentration of a reactant decreases, there are fewer of that particles present, and the rate of reaction decreases (Sciencing, n.d.). This means that the time taken for a reaction to occur could differ; certain tests could take longer than 24 hours to react.

Maybe if we had waited longer, or if we had observed over a larger time span, there could have been evidence of further change. In the future, we should be more precise with our measurements and we should observe our results for more then one day; this would result in more accurate findings. Furthermore, the tests were left overnight in an unsterile environment; the environment was not free from germs or microorganisms. It is possible that bacteria and other microorganisms entered our test tubes. If this occurred, it could have significantly impacted our final results; it could have altered the colour of our products. The colour was the main observation in this lab; therefore, if the colour is altered, our final results are affected as well. In the future, it would be better to do such a lab in a more sterile environment; this will result in more accurate results as well. In addition to that, the solid metals used in these tests could have been non-sterile as well. For example, it is possible that the iron nail used in test number 3 was not pure iron; perhaps there were certain bacteria or microorganisms present on the nail. When this nail is put into the solution, it could also alter the colour and impact our final results.

This does not only apply to the iron nail; other bacteria or microorganisms could have been present on the copper wire, aluminum, zinc, and tin as well. Thus, in the future, it is essential to complete this lab in a more sterile environment for more accurate results; the materials used should be sterile as well. Moreover, in the future, it would be beneficial to do some research before starting a lab as well; it will enhance the overall understanding of the lab. For example, researching the elements involved in the reaction and their properties could be significantly beneficial; it allows for the consideration of certain anomalies. For instance, tests number 2 and 5 did not proceed as anticipated; they were inconsistencies. Researching before these tests would have prevented any confusion.