INTRODUCTION
In this experiment our objective is to investigate how chemical properties of different substances react with substances with different chemical properties.
In this laboratory experiment we focused on making and recording observations about chemical properties in reactions that give easily describable results such as change in temperature, gas/bubble formation the production of precipitates and also appearance and disappearance of a metal in contact with a solution containing its metal ions. Using the data collected we will attempt to prove the hypothesis that some chemicals can replace another chemical in a compound because it is more active. At the end of this experiment we will be able toe present the chemicals in an order according to their activity.
There are many types of reactions that occur in the environment. Oxidation reduction reactions which breaks down into combination reactions, where two or more substances combine to form a single product, decomposition reaction, which is the breakdown of a compound into two or more components and combustion reaction, which is a reaction in which a substance reacts with oxygen.
DSC01964 - Copper reactions
DSC01977 - Magnesium (II) reactions
Zn(NO3)2Combination reaction: A + B AB
Decomposition reaction: AB A + B
Combustion Reaction: C + O2 CO2
There are other reactions where a compound is reaplaced by an ion of another element. These are called displacement reactions. Displacement reactions are brokendown into 3 different sub categories.
Hydrogen Displacement: Ca + 2H2O Ca(OH)2 + H2
Metal Displacement: Zn + 2HCl ZnCl2 + H2
Halogen Displacement: Cl2 + 2KBr 2KCl + Br2
All the above-mentioned reactions will be tested to prove the hypothesis of activity of metals and to obtain a idea of which metals have a higher activity and which metals have a low activity.
MATERIALS
24 well plates
Test tube
Transfer Pipette
Beakers
Measuring Test tube
Wooden splint for burn test
Metals (Zn, Cu, Fe, Mg, Ag)
Nitrate Solutions (AgNO3, Cu(NO3)2, Zn(NO3)2, Mg(NO3)2, Fe(NO3)3, KNO3)
Solutions (NaCl, Na2S, NaOH)
HCl Acid
Distilled Water
Carbonates (Na2CO3, K2CO3, CaCO3, MgCO3)
METHOD
There were several parts to this laboratory experiment where we combine several chemicals with other chemicals to see the outcome. Firstly we made a table to write down observations that are made.
PART 2
In this part we tested a group of nitrate solutions with a couple of different solutions. We filed a 24 well plate with 1ml of AgNO3, Cu(NO3)2, Zn(NO3)2, Mg(NO3)2 and Fe(NO3)3 . Each of these nitrates were then mixed with 1ml of NaCl, Na2S, NaOH and Na2CO3 respectively. The solutions were added to each nitrate only after observations were made. Each combination of solutions was carefully observed for any signs of reactions. The observations were then recorded in a table. Extreme care was taken not to let each solution mix with the one next to it as this will create inaccurate and confusing results.
PART 3
In this part of the experiment we used a correctly labeled 24 well plates with one row with 2ml of HCl and the second row with 2 ml of H2O. We added one piece of metal to each well with HCl and H2O and recorded the observations that we made after sufficient time was given for the reactions to happen. Each column of HCl and H2O had Zn, Cu, Fe, Mg and Ag as the metals.
PART 4
In this part of the experiment we tested the reaction of carbonate compounds with acid and water. We selected HCl as our acid and distilled water to mix with the carbonates. Similarly to part 3 we used a 24 well plate with one row of each HCl and H2O with one well holding 2 ml of solutions respectively. Small amounts of NaCO3, K2CO3, CaCO3 and MgCO3 were added to each of the wells containing HCl and H2O. Careful observations were made each time a carbonate was added to the respective solutions. A table was made to write down the observations that reflected the way the 24 well plate was set up.
PART 5
In this part of the experiment we used two 24 well plates to add the metals Ag, Cu, Fe, Mg and Zn to AgNO3, Cu(NO3)2, Zn(NO3)2, Mg(NO3)2, KNO3 and Fe(NO3)3. Each column was dedicated to a specific nitrate and each row was dedicated to a single type of metal. This way it was easier to keep track of each chemical as we looked for evidence of reactions and observations. Each well was observed for sings of a chemical reaction and all observations and findings were recorded in a table that was arranged to reflect the way the two 24 well plates were arranged.
RESULTS AND DATA
PART 2
The following table shows us the reactions between 4 known compound solutions with 5 known nitrate solutions and their respective observations.
AgNO3, | Cu(NO3)2 | Zn(NO3)2 | Mg(NO3)2 | Fe(NO3)3 | |
NaCl | Clear solution. White solid precipitate was observed. | No change | No change | No change | No change |
Na2S | Solution turned black | Dark black solution | Very light white solution | Solution turned a light white | Solution turned dark black initially and then turned into a light yellow solution |
NaOH | Solution turned light brownish color. Brown precipitate was observed. | Light blue precipitate was observed. | White precipitate was observed. | Light white precipitate was observed | Yellow/orangish precipitate was observed. |
Na2CO3 | Milky white solution. Light white solid precipitate was floating on the surface of the solution | Dark bluish/greenish solution. | Light white solution | Very light/milky solution | Solution turned orangish. Bubble formation was seen after a couple of minutes. |
Table 1
With the above shown reactions we predict that some of the mixtures will make precipitates and some of them will not due to their solubility properties. We also predict some will not react at all supporting out hypothesis of activity.
PART3
The following table shows the results and observations when 5 knows metals were mixed with HCl acid and H2O (Distilled Water).
Zn | Cu | Fe | Mg | Ag | Na | |
HCl | Bubble formation, Warm | No reaction. No gas formation. No change in temperature. | Slow bubble formation. No heat was detected. | Rapid bubble formation. Metal completely disappeared. High reaction speed. | No reaction was seen | Very rapid bubble formation. Na strip completely dissolved. Started burning during reaction. Visible gas release. |
H2O | White residue on the metal. No bubbles, no heat changes. | No reaction was seen | No reaction was seen | Light Bubble formation. Some sort of oxidation on the surface of the Mg piece. | No reaction was seen. | Bubble formation. Na strip completely dissolved in the solution. Swooshing sound during reaction. |
Table 2
In the above-illustrated reactions between metals and HCl we expect hydrogen gas release and no precipitates. For the reactions with H2O we also expect to see hydrogen gas release from some reactions but not all. The Na and Mg reactions were also subjected to a flame test to find which gas was released. The instructor conducted the flame test.
PART 4
The following table illustrates the observations and results when 4 known metal carbonates were mixed with HCl acid and H2O. (Distilled Water)
Na2CO3 | K2CO3 | CaCO3 | MgCO3 | |
HCl | High reaction rate, high rate of bubble formation, the carbonate completely dissolved in the solution. | High reaction rate, the carbonate completely dissolved, high rate of bubble formation. Drop in temperature. | High reaction rate, no change in temperature was noted, high rate of bubble formation, carbonate completely dissolved in the solution | Rapid bubble formation was observed, slower rate of reaction; carbonate did not dissolve completely, no change in temperature. |
H2O | No bubble formation, no change in temperature, slow reaction speed. | Slow reaction speed. No bubble formation was seen; no change in temperature was noted. | Slow reaction speed. Little bubble formation was seen; carbonate did not dissolve completely and was seen in the solution. | No reaction was observed, no change in temperature, no bubble formation. The carbonate was observed to just sink to the bottom of the solution. |
Table 3
In the above mentioned reactions we suspect that H2O and CO2 were by products. We also believe there will be no precipitates due to chlorides are completely soluble.
PART 5
The table below shows the observations and results we acquired where we combined known metal nitrate solutions with 5 types of known metals.
Ag | Cu | Fe | Mg | Zn | |
AgNO3 | Lost its shininess, no bubble formation, no change in temperature. | Solution turned dark blackish, there was a light white buildup on the surface of the Cu. | No reaction observed. | Blackish build up on the surface of the metal. The build up broke off the metal when shaken. | Highly reactive, turned black and a dark blackish residue was observed on the surface of the metal, solution remained clear. |
Cu(NO3)2, | No reaction | No reaction | Loss of shininess, no further change was observed. | Greenish precipitate was observed floating on top and at the bottom of the solution, Metal dissolved completely | Bubble formation, metal turned black. |
Zn(NO3)2 | Loss of shininess, no bubbles or change in the solution. | No reaction | No reaction | Bubble formation, metal did not dissolve completely. | Very light oxidation like build up on the surface of the metal. |
Mg(NO3)2 | No reaction. | No reaction. | No reaction. | Bubble formation around the cut edges of the metal | Some oxidation like buildup on the surface of the metal |
Fe(NO3)3 | No reaction. | Metal turned dark brown, solution turned dark brown with a dark brown precipitate at the bottom of the solution. | No reaction. | Dark orangish precipitate at the bottom of the solution. Bubble formation was observed on the surface of the metal, like rust build up on the surface. | Solution turned dark orangish. Loss of shininess, rust like build up on the surface of the metal. |
KNO3 | No reaction. | No reaction. | Loss of shininess. No further changes were observed. | No reaction. | No reaction. |
Table 4
The above reactions are suspected to make nitrates only if their activity is higher than of the metal that its reacting with. d
DISCUSSION
In part 2 when the nitrate solutions were dissolved with NaCl, Na2S, NaOH and Na2CO3 there were several different observations that we made. When NaCl was mixed with AgNO3 we have the following chemical reaction occurring.
AgNO3 + NaCl AgCl + NaNO3
This reaction is called a double replacement reaction, where Ag and Na are interchanged as shown in the equation. In this reaction both reactants are in the liquid form initially but in the result we saw a white precipitate at the bottom of the solution. We identified this precipitate as AgCl. NaCl was mixed with another four metal nitrates (Cu(NO3)2, Zn(NO3)2, Mg(NO3)2 and Fe(NO3)3) but no other precipitates were observed. Below are the reactions between NaCl and the metal nitrates.
Cu(NO3)2 + NaCl CuCl2 + NaNO3
Zn(NO3)2 + NaCl ZnCl2 + NaNO3
Mg(NO3)2 + NaCl MgCl2 + NaNO3
Fe(NO3)3 + NaCl FeCl3 + NaNO3
In all the reactions above no precipitate was observed. This is explained by the solubility rules where the metal halide products and the NaNO3 are all completely soluble. Therefore no precipitates were observed.
This was not the case with the other combined mixtures that we made in this part, which contained Na2S, NaOH and Na2CO3. When mixed with metal nitrates at the sulfide, hydride and the carbonate products showed up as precipitates because they are insoluble compounds.
In part 3 of the experiment five known metals were added to solutions of HCl and H2O respectively. From the observations that were made Zn, Fe, and Mg metals had strong reactions when mixed with HCl. We also observed high rate of formation of bubbles. Another interesting observation was that there was no precipitate formation as a product of these reactions.
Zn + 2HCl ZnCl2 + H2
Fe + 2HCl FeCl2 + H2
Mg +2HCl MgCl2 + H2
From the above reaction equations we understand the bubble formation occurred due to the release of hydrogen (H2) gas as a product of the reaction. Therefore above like reactions are also called hydrogen displacement reactions. There were also no precipitates observed due to the fact that Cl- compounds are highly soluble. Another interesting observation was that there was no reaction between the HCl and Cu and Ag. These phenomena can be used to explain our hypothesis of the activity series. Inability of Cu and Ag to displace H from HCl can be explained as these aforementioned metals are less active that hydrogen. Therefore from this part of the experiment it can be deduced that in terms of activity Mg, Fe, Zn > H > Cu and Ag
Above mentioned metals were also mixed with water. From prior observations it can be explained why we did not see any reaction occurring between H2O and Cu and Ag. Interesting observation in this part was we didn't see such a visible reaction between H2O and other metals either. Mg, Fe and Zn all had some sort of visible layer on top of its surface, which are their respective hydroxides. These were visible in the solution due to their insolubility.
Zn + 2H2O Zn(OH)2 + H2
In part 4 as shown in the table 3 four different known carbonates were mixed with HCl and H2O. The carbonates reacted fast and created a large number of bubbles and also a visible gas formation was also observed. The below reaction equation is an example of the reaction that took place. We also observed that all the solid carbonates did disappear indicating that all of the carbonate reacted with the HCl.
Na2CO3 + 2HCl 2NaCl + H2O + CO2
We observed this reaction as a fast highly active reaction. From earlier experiments it was deduced that metals such as Na, K, Ca and Mg all have a higher activity than Hydrogen (H). This is one reason that this reaction occurs very quickly. The reason for the solution having no precipitates is the solubility of NaCl. Alkaline metals and halides are highly soluble elements. This is true for all the carbonates that we used in this experiment hence the reason for us observing no precipitates after these reactions has occurred. Unlike in the reactions between metals and HCl where it was observed that H2 gas was formed, when carbonates reacted with HCl we observed that CO2 was produced along with H2O. The identity of the gas was confirmed by holding a burning splint over the reaction. The result was the burning stick stopped burning as the gas hit it confirming the presence of CO2.
When the carbonates were added to H2O observations was a slower reaction speed than the ones observed earlier with HCl. All of them presented with little bubble formation indicating the release of gas that we confirmed was CO2 with the aid of a burning stick. Na2CO3 and K2CO3 did not leave a precipitate but CaCO3 and MgCO3 did leave some sort of precipitate in the solution. This can be explained again by the rules of solubility.
Na2CO3 + H2O NaOH + CO2
NaOH being a compound with a hydroxide and a alkali metal is a completely soluble compound as opposite to the reaction between MgCO3 and H2O.
MgCO3 + H2O Mg(OH)2 + CO2
Where Ca(OH)2 is an insoluble hydroxide which explains the precipitate in the solution. From the observations made now we can deduce that based on activity of metals that Na,K,Ca >Mg.
In part 5 as shown in table 4, 6 known metal nitrates were mixed with 5 known metals. When the nitrates are considered AgNO3 reacted with all the metals with Ag being displaced. This concluded that when all the metals considered in this experiment Ag is the least active metal in this group since it was displaced from the nitrate by all the other metals.
2AgNO3 + Cu Cu(NO3)2 + 2Ag
Therefore Cu, Fe, Mg, Zn > Ag
Cu(NO3)2 reacted only with Fe, Mg and Zn. Mg in fact was completely disappeared from the solution indicating that it reacted quickly with the nitrate.
Cu(NO3)2 + Mg Mg(NO3)2 + Cu
Therefore we can deduce that Mg, Fe, Zn > Cu > Ag
Zn (NO3) 2 reacted only with Mg, where at the end of the reaction some of the Mg was left behind. The observed reaction give us the result that Mg is capable of displacing Zn from the nitrate and making a nitrate with itself.
Zn(NO3)2 + Mg Mg(NO3)2 + Zn
Hence we can deduce that Mg > Zn> Fe> Cu> Ag
We proof for the afore mentioned inequality is found in the reactions between Fe(NO3)2 and metals where we saw clear reactions only when Mg and Zn were added. One of the surprising observation made was that when Cu was added to Fe(NO3)2, the Cu turned dark brown and so did the solution. This observation contradicts the results that we have observed so far. After discussion with the group and compared with other results it was deduced that this could have been due to an error or due to a misstep that occurred while performing the experiment and it was decided that we discard the observations made in this reaction.
The most interesting observation was made when the metals were mixed with a solution of KNO3. No clear reactions were observed. The only observation made was that the Fe metal did loose some of its shininess after a week, which was deduced as some sort of external reaction that had nothing to do with the reaction with the nitrate.
Ag + KNO3 No reaction.
Cu + KNO3 No reaction
Fe + KNO3 No reaction
Mg + KNO3 No reaction
Zn + KNO3 No reaction
Therefore it can be deduced K > Mg > Zn> Fe> Cu> Ag
INSTRUCTORS EXPERIEMNT
An experiment was performed by Dr. Taylor to illustrate the hydrogen displacement reactions and also to teach the students how to identify what type of gas is released in an experiment using the burn stick method.
4 test tubes were used where 2 of them contained HCl and the other 2 contained distilled H2O. Initially a Mg strip was added to the first test tube with H2O and was observed. No reaction or gas formation was observed. Then a Mg strip was added to one of the test tubes containing HCl. Observation included a high reaction speed and high rate of bubble formation indicating gas formation. A burn stick experiment was performed to identify the gas and the burning stick made a pop sound indicating the existence of hydrogen gas. Another observation made was that water vapor was found on the inside of the test tube after the burning stick.
Mg + 2HCl MgCl2 + H2
After burning stick experiment
2H2 + O2 2H2O
As an added step Phenolphthalein, a PH indicator, was added to the test tubes to identify the range of PH value of the solution after the reactions. When Phenolphthalein was added to the test tube with Mg and H2O the solution turned a pinkish color (fuchsia). When Phenolphthalein was added to the test tube with HCl and Mg there was no color change. Therefore a drop of Methyl Red, another PH indicator for acids, was added to the solution, which gave it a yellow/orangish color to the solution indicating the presence of acid with a high PH value.
Mg + H2O+ Phenolphthalein Mg + HCl + Methyl Red
Next we added a strip of Na to the remaining test tube with HCl. Observations included a violent reaction which included the Na strip burning with a bright flame inside the test tube and a loud pop and the presence of water vapor inside the test tube after a burning stick was help over the test tube indicating the formation of hydrogen gas. Phenolphthalein was added to the solution to check the PH value of the solution that resulted in a clear solution indicating the acidic PH in the solution. Therefore a methyl red was added to the solution that gave the solution an orange color, an indication of high acidic PH value.
When Na was added to the test tube with H2O we observed a reaction that resulted with bubble formation and the Na strip being completely reacting with the water. We also observed a "swooshing" sound during the reaction indicating the high activity of the Na metal. A burn test was performed to identify the gas that was released as a product. The "pop" sound and the formation water vapor post burn test confirmed the presence of hydrogen gas as a product of this reaction. Phenolphthalein was added to the solution post reaction, which gave the solution a pink/reddish color indicating that the solution has a base PH value.
Na + H2O + Phenolphthalein Na + HCl + Methyl Red
When the reaction speed, bubble formation and other observations taken into consideration it can be deduced that Na has a much higher activity than Mg. therefore from this experiment we deduced that when activity is considered Na > Mg
CONCLUSION
When we consider all of our observations and discoveries we can clearly perceive that chemicals react with each other and other solutions according to their activity. A chemical compound has the ability to displace another chemical compound if it s activity is higher than the other which we call displacement reactions. This confirms our hypothesis that we made initially in the beginning of this this experiment. From the results that we have obtained in this experiment all the chemical substances can be arranged according to their activity. The result is as follows.
K > Na > Ca > Mg > Zn > Fe > Cu > Ag
REFERENCES
"Chemistry" 10th Edition by Raymond Chang, Chapter 4 " Reactions in Aqueous Solutions"
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