metal-metal displacement

INORGANIC CHEMISTRY 1

Lab Report on
Oxidation & Reduction
I. Metal-Metal Ion Displacement
II. Halogen Displacement Reactions

INTRODUCTION
A series of experiments had been conducted to determine the order of displacement strengths of the metals and halogen chosen for the experiments. A displacement reaction is a reaction in which one element(metal or non-metal) displaces another element(metal or non-metal) from its salt solution. In the displacement reaction of metals, the more electropositive metal will displace the less electropositive metal from its salt solution Through the observations of experiment results, aligning them with theory, oxidizing and reducing agents are distinguished.

DISCUSSION
Part A: Metal-Metal Ion Displacement Reactions

In the first set experiments involving metal-metal ion displacement metal-nitrate solutions were prepared first. Using the formula:
Molarity=moles of solute liters of solution
This formula was used in order to calculate the amount of metal-nitrate in grams that were needed to be weighed to produce the wanted metal-nitrate solutions. Below are the calculations involved for each metal

Mg(NO3)2
0.1M x 0.05L x 256.14gmol-1 = 1.2807 g
Zn(NO3)2
0.1M x 0.05L x 297.0 gmol-1 = 1.4850g
FeSO4
0.1M x 0.05L x 151.92gmol-1= 0.7596g
Pb(NO3)2
0.1M x 0.05L x 331.22gmol-1= 1.6561 g
Cu(NO3)2
0.1M x 0.05L x 230.02 gmol-1 = 1.1501 g

OBSERVATIONS Mg(NO3)2
Zn(NO3)2
FeSO4
Pb(NO3)2
Cu(NO3)2
Mg Metal

Dark tiny substances (presumably Zn metal) dull the surface of Mg ribbon. Solution remains clear
Tiny dark chunks of Fe metal formed on Mg surface. The yellow color of solution eventually fades
Very small black bits of Pb metal formed on Mg ribbon surface
Small amounts of Cu metal bits on Mg surface was observed, the intensity of the blue-colored solution reduced
Zn Metal
No observable change occurred

The yellow color of solution eventually fades. Very tiny Fe metal deposited on Zn metal granules
Small amounts of tiny dark Pb metal deposits were observed on Zn metal granules.
The prominent blue color of solution fades. Very small amounts of Cu metal can be seen among the Zn granules
Fe Metal
No observable change occurred
No observable change occurred

No observable change occurred. (Which is contrary to theory, will be further explained in discussions)
The blue-colored solution loses its color intensity
Pb Metal
No observable change occurred
No observable change occurred
No observable change occurred

The blue-colored solution loses its color intensity
Cu Metal
No observable change occurred
No observable change occurred
No observable change occurred
No observable change occurred

(Note: All half-equations & overall equations that support the observations are located at the end of discussions)
When Mg metal was placed into a solution of Zn(NO3)2 it had been observed that dark-colored tiny Zn metals dulled the surface of the Mg ribbon. The reason for this observation is because, Mg metal is a stronger reducing agent compared to Zn, therefore Mg has to ability to displace Zn2+ ion. While in a solution of FeSO4 tiny dark chunks of Fe metals can be seen on the Mg ribbon, which is accompanied by the decolourization of the yellow-colored solution resulting in a paler yellow solution (know that the yellow color of the FeSO4 is due to the presence of Fe2+). This also proves that Mg metal is more reactive than Fe metal. Next, in a solution of Pb(NO3)2 , Mg metal was able to displace Pb2+, since based on the observation little bits of Pb metal can be seen on the surface of Mg ribbon. Lastly in Cu(NO3)2 decolourization of the blue-colored solution was observed, this is due to the displacement of Cu2+ by the more reactive Mg metal (know that the blue colored solution is due to the presence of Cu2+ in Cu(NO3)2 solution)

As for the next metal, Zn metal, when placed into Mg(NO3)2 solution, there was no observable change, thus an indication that no displacement of metals is occurring. This is because, Zn metal, is lower in reactivity compared to Mg. In a solution of FeSO4, the intensity of the yellow colored solution reduces with the addition of Zn metal. This indicates that Zn was able to displace Fe, therefore Zn metal can be said to be a stronger reducing agent compared to Fe. Zn metal was then added into a solution of Pb(NO3)2. Based on the observations, tiny pieces of metal can be detected however the amount was so puny that it took quite a while to see it. Thus, Zn metal successfully displaced Pb making it a more reactive metal. Lastly, in a blue-colored Cu(NO3)2, the solution the color intensity was reduced, thus indication that Zn metal is more reactive, allowing it to reduce Cu.

The third metal involved is Fe metal. In both Mg(NO3)2 and Zn(NO3)2 solution there was no observable change, this shows that Fe metal has low reactivity thus disallowing it to displace Mg and Zn. In a solution of Pb(NO3)2 theoretically very small bits of Pb metal was to be formed on Fe metal granules. This would prove that Fe metal is higher in reactivity compared to Pb allowing it to carry out displacement. However in the experiment carried out, there were no metal bits observed, this was probably because the metals were so tiny in size that the human naked eye is unable to distinguish Fe metal from Pb. Finally Fe metal was placed in a solution of Cu(NO3)2, the intensity of the blue-colored solution was reduced, this indicates that Fe metal had displaced Cu making Fe metal the more reactive metal,

As for Pb metal, when placed into solutions of Mg(NO3)2 , Zn(NO3)2 , and FeSO4 there was no observable change, no reaction was occurring therefore it proved that Pb metal is not strong enough to displace Mg, Zn and Fe. However when placed into a solution of Cu(NO3)2, it was observed that the intensity of the blue-colored solution reduced thus indicating that Pb metal has a higher reactivity compared to Cu thus displacement by Pb metal was possible.

Lastly, Cu metal was placed into solutions of Mg(NO3)2 , Zn(NO3)2 ,FeSO4 and Pb(NO3)2. No reaction occurred for all, as there were no observable changes. This showed that Cu metal is the least reactive metal out of the 5 metals since it is unable to displace any of them.

To conclude, the arrangement of metals in the order of decreasing strengths is as below:
Mg>Zn>Fe>Pb>Cu

Part B: Halogen Displacement Reactions
DISCUSSIONS
Each halogen were added into 2mL of dichloromethane to produce each of the individual halogen colours. These are used as control experiments, in order to compare experiment results to the original halogen colors. Colours of control experiments of each halogen are as below:
Chlorine: 2 layers formed. The dichloromethane layer provides a colourless solution
Bromine: 2 layers formed. The dichloromethane layer provides an orange solution
Iodine: 2 layers formed. The dichloromethane layer provides a purple solution

OBSERVATIONS

KCl(aq)
KBr(aq)
KI(aq)
Cl2(aq)

Colourless solution formed
Colourless solution formed
Br2(aq)
Brown solution formed

From brown to purple solution formed at the bottom layer of the 2-layered solution
I2(aq)
Purple solution formed
Purple solution formed

Cl2(aq) + KBr(aq)  KCl(aq) + Br2(aq)
Based on the above equation, Cl2 had successfully displaced Br- thus as proven by experiment observations, Br2 was formed. The presence of Br2 was indicated by the brown solution formed.
Cl2(aq) + KI(aq)  KCl(aq) + I2(aq)
Based on the above equation, Cl2 had successfully displaced I- thus proving that Cl2 is a stronger oxidizing agent compared to Iodine. This is proven by the change color from colorless to purple solution.
Br2(aq) + KCl(aq)  no reaction
This is because Br2 is a less reactive halogen compared to chlorine, thus Br2 is unable to displace Cl-. This was proven as the brown colored solution was obtained.
Br2(aq) + KI(aq)  KBr(aq) + I2(aq)
In this reaction brown solution turned purple due to the presence of I2. This proves that Br2 is stronger oxidizing agent thus able to displace Iodine.
I2(aq) + KCl(aq)  no reaction
I2(aq)+ KBr(aq)  no reaction
As shown in the above equation, it can be seen that in both KCl and KBr, no displacement is occurring; this is due to the fact that I2 is not strong enough to displace chlorine and bromine from its compound. This was proven through the experiment results as it showed that purple solution was formed, indicating presence of I2
Based on the experiment results, the order of the strength of halogens as oxidizing agents can be determined.
Cl2>Br2>I2
Halogens exist as diatomic molecules that interact through dispersion forces. This dispersion forces increases in strength as the atom becomes larger. This trend of oxidizing ability decreasing down the group can also be explained in terms of electronegativity, whereby as you go down the group, EN decrease, the halogen atom pulls electrons less strongly making it a less strong oxidizing agent