The universe is built upon chemical reactions. There are simply so many chemical reactions that change how we live, from the nuclear reactions in the Sun, to photosynthesis and digestion.
Although every chemical reaction known is important for human survival, there are many types of chemical reactions ranging from nuclear to combustion. A single displacement reaction is a type of chemical reaction where an element takes the place of another within a compound. This reaction is commonly shown as:
AB(aq) + C ⟶ CB(aq) + A
In this reaction, A and C would be pure elements and exist as a solid or gas, depending on what the pure element exists as. On the other hand, the compounds AB and CB are aqueous solutions. In most cases, a single displacement reaction would take place between metals which have a positive charge they are willing to give away. The difference between these metals would be their reactivity which would determine which metal would stay in its pure elemental form or bond in the solution.
A single displacement reaction could only take place if the pure elemental reactant has a higher reactivity than the positive ion in the aqueous solution. In this case, C would have to have a higher reactivity to be able to take A’s position in the aqueous solution. This is where the activity series would be of help, as chemists would be able to determine if the reaction would actually occur, based on if the element C is higher than A on the chart. For example, copper is very low on the activity series compared to aluminum, which would replace the copper ions in an aqueous solution.
What is the order of reactivity of the metals copper, magnesium, and zinc in single displacement reactions with an assortment of solutions?
This lab aimed to test the reactivity of copper, magnesium, and zinc metals with different solutions. The results would then create an activity series demonstrating the metals’ tendencies to react in chemical reactions. The solid metals were placed in various metal ion solutions to determine if a reaction would occur. The metals were then ranked based on the observations.
If solid metal pieces are placed in one certain solution, then the metal that is highest on the activity series would react the most, if at all, because of its high reactivity.
➔ 7 small pieces of each of the following metals: copper wire; Cu(s), magnesium pieces; Mg(s), and zinc powder; Zn(s)
➔ dropper bottles containing dilute solutions (0.1 mol/L) of :
- Copper (II) sulfate, CuSO4(aq)
- Zinc sulfate, ZnSO4(aq)
- Hydrochloric acid, HCl(aq)
- Magnesium sulfate, MgSO4(aq)
- Iron(II) sulfate, FeSO4(aq)
- Tin(II) sulfate, SnSO4(aq)
➔ Two 15-well reaction plates
➔ Squirt bottle with distilled water
- Cleaned the three metal pieces with sandpaper.
- Placed cleaned copper piece into first well in reaction plate.
- Placed 5 drops of zinc sulfate into the first well in the reaction plate.
- Recorded if reaction happens in solution in the observations table.
- Repeated steps 2-4 in different wells with the other 6 solutions: copper (II) sulfate, magnesium sulfate, tin (II) sulfate, iron (II) sulfate, water and hydrochloric acid
- Placed cleaned magnesium metal piece onto second row of reaction plate
- Repeated steps 3-5 for magnesium metal on second row of reaction plate
- Placed clean zinc metal piece onto third row of reaction plate
- Repeated steps 3-5 for zinc metal on third row of reaction plate
- Cleaned station, returned materials, and emptied reaction plate
Table 1.1: Qualitative observations on reactivity of metals.
Figure 1.1: Activity Series obtained through experimental observations
Balanced Equations of the Observations
Table 2.1: The balanced chemical reactions of each metal with each solution
|Mg + ZnSO4 → MgSO4 + Zn||Zn + MgSO4 → NR||Cu + ZnSO4 → NR|
|Mg + CuSO4 → MgSO4 + Cu||Zn + CuSO4 → ZnSO4 + Cu||Cu + MgSO4 → NR|
|Mg + SnSO4 → MgSO4 + Sn||Zn + SnSO4 → ZnSO4 + Sn||Cu + SnSO4 → NR|
|Mg + FeSO4 → MgSO4 + Fe||Zn + FeSO4 → ZnSO4 + Fe||Cu + FeSO4 → NR|
|Mg + 2HCl → MgCl2 + H2||Zn + 2HCl → ZnCl2 + H2||Cu+ HCl → NR|
|Mg + H2O → NR||Zn + H2O → NR||Cu + H2O → NR|
The activity series that has been observed from this lab places magnesium, zinc, iron, tin, hydrogen, and copper from most to least reactive. In this activity series, any element above another could react and replace the lower element in a single displacement reaction, but an element cannot react and replace an element higher than it.
Magnesium is the most reactive element out of the 6 elements that need ranking. This is because it has the most violent reactions and the magnesium metal reacts with every solution. The magnesium sulfate solution does not make a reaction with zinc or copper, further proving that magnesium is the highest on the activity series. This concludes that magnesium is the highest.
Second on the activity series would be zinc as the metal reacts with every solution other than magnesium. On the other hand, the zinc sulfate solution only reacted with magnesium too further proving that zinc is second on the activity series, placing the rest below it.
Third on the activity series would be iron as it reacts slightly with magnesium and zinc compared to tin and hydrogen. As the three elements iron, tin and hydrogen react with only magnesium and zinc, we have to turn to the qualitative observations recorded on the observation table (Table 1.1). The reaction that iron makes with magnesium and zinc is very slight meaning it is the most reactive out of the three.
The fourth metal on the activity series would be tin, which reacts only with magnesium and zinc. As per the qualitative observations in the table, tin has a weaker reaction than hydrogen does but a stronger one than iron. This means it is placed fourth on the activity series.
Fifth on the activity series is hydrogen, where hydrochloric acid reacts violently with both magnesium and zinc, but no reaction with copper. This means that hydrogen ranks above copper but below every other metal in the list.
Last and least reactive on the list would be copper which reacts with none of the solutions, and the copper solution is the most reacted with. This means copper is easily replaceable in single displacement reactions and is not high on the activity series at all.
The control, water, also did not react with any of the metals even though they reacted with the hydrochloric acid. The reasoning behind this is because the bonds are much stronger in water and it is also a solvent. Also a reaction between a metal and water creates a hydroxide, which
prevents any other reaction from tracking place (single displacement).
Sources of Error
The sources of error in this experiment range from systemic errors to random errors that could both affect the outcome. Firstly, a major systematic error would be leftover oxidation on the metals as the metal pieces used in this experiment were too miniature to clean with sandpaper. This oxidation layer on the metals may cause a firm barrier between the metal and the solution, making no reaction possible. Secondly, there was no precise measurement related to the metals as the pieces were small and irregular and not measured at all. This could lead to a different result as more metal could have the possibility of more violent or visible reactions, causing a slight error. Lastly, the equipment was not brand new nor sanitized from previous uses, meaning it could be contaminated. On top of that, the actual solutions could be contaminated or there could have been a possibility of evaporation for some solutions resulting in mismatched molar concentrations.
The activity series created from the observations of this experiment matched the original activity series and the hypothesis was proven correct. The elements were also ranked based on how much they reacted with other elements below their reactivity. This experiment successfully demonstrated the original activity series and how it could be useful.