EXPERIMENT: IONIC REACTIONS 8
This experiment focused onstudying and applying the nature of ionic reactions. The experimentalso aimed at writing balanced equations for the ionic substanceequations. It was also the goal of this experiment to analyze and getan effective view of the results from the reactions. Through thevarious experiments in the laboratory, I was in a position to clearlyidentify some of the characteristics of anions, as well as those ofcations. In the laboratory, I carried out the flame test experiment,which enabled me to identify the cations. Additionally, through thetest, I was able to find out the reactions between anions and ioniccompounds.
Experiment and Observation:
Experiment one involved aqualitative anion test which was done through the observation ofvarious chemical reactions. The results from this test have beenrecorded in the data table labeled as 1. The test providedinformation that enabled me to identify various unknown substances.The results from this experiment were clearly recorded in the datatable labeled 1. It is useful to state that the procedure used inthis experiment was adapted from the Anions, Cations, and IonicReactions LabPaq Lab manual. It is vital to refer to this manual forany extra information regarding the experiments.
Data Table 1: AnionConfirmation Tests
Chemical | Anion | Additionof AgNO3 | Addition of HCl |
NaBr | Bromide | Cloudy whitethin solution | Clear with sedimentation |
Na2CO3 | Carbonate | Clearwith white sedimentation | Bubbles, sedimentation combined to oneformation |
NaCl | Chloride | Milkywhite, white sedimentation | No visible change |
Nal | Iodide | Pale greencloudy, sedimentation | Sedimentation dispersed to smaller pieces,solution clears in color |
Na2SO4 | Sulfate | No visiblechanges noted | Milky white |
Na2S | Sulfide | Clear withamber sedimentation | No visible Change noted |
Unknown #103 |CarbonateNa2CO3 | Cloudy white thin solution | Bubbles, Sedimentationcombined to one formation |
Unknown #104 | ChlorideNaCl |Clear with amber sedimentation | No Visible Change |
The second experimentrequired the performer to be extremely cautious with the safetyprecautions. It was an experiment to find out the qualitative cationtesting through the flame. I ensured that all the standard andrecommended safety precautions were followed during the experiment.The experiment followed the procedure of observing the changes in thecolor flames with known substances. The results were clearly recordedin the data table number 2. Additionally, the information obtainedfrom the flame color changes was used to identify the unknownsubstances. The results obtained from this observation were recordedin the data table number 2 for referencing.
Data Table 2: Cation FlameTests
Chemical | Cation | FlameObservations |
Kl | Potassium | Light purple |
CaCl2 | Calcium | red tintnoted |
LiOH | Lithium | Dark red,almost crimson |
NaCl | Sodium | BrightYellow |
Cu(NO3)2 | Copper | KellyGreen |
Unknown # 105 | Copper |Kelly Green |
Unknown # 106 | Potassium |Light purple |
Unknown # 107 | Lithium |Dark Red |
The information obtained fromthe above experiments and the results found were extremely essentialfor this stage. The information obtained helped in determining thechemical compositions of the elements. The information from theprevious experiments was essential in determining the names of thechemicals in question as well as their formulas which were given.This data was recorded data table 3 as shown below.
Data Table 3: CompleteChemical Identification
Chemical | Cation | Anion TestObservations | Anion | Complete Chemical Name and Formula |
Unknown #105 | Copper | Clearwhite sedimentation with AgNO3, bubbles with HCl | Carbonate | CoppercarbonateCuCO3 |
Unknown #106 | Potassium |yellow with AgNO3, No change with HCl | Chloride | PotassiumchlorideKCl |
Unknown #107 | Lithium |Cloudy white with AgNO3, Clear with sedimentation change with HCl|Bromide | Lithium bromideLiBr |
Calculation and Error:
It is essential to note thatthis experiment required no calculations and therefore there were nocalculations done whatsoever. More often than not, an error canemanate from contamination since there were utensils used to open thevarious chemicals. Additionally, it is evident that the flame colordepends on the ability of the person to identify the color perfectly.Consequently, it can be extremely difficult for people who are colorblind to identify the colors. It is also useful to state that therewere no measurements that were done in this experiment and thereforechances for measurement errors are absent. The procedure for theexperiment did not require any measurements.
Discussion and Conclusion:
Identification of chemicalscan be a tedious and long process in the lab. However, the use of thecation flame test and the anion confirmation test made it extremelyeasy to identify the chemicals. The only valuable skill was observingthe chemical reactions of the ion. After observing the results, itwas easy to identify the properties of the unknown substances.Recording of the data and information for every step in theexperiment is extremely vital as it ensures that such data andinformation can be used as reference in the future. These experimentscan help someone with an unknown chemical substance to identify thechemical components of the substance. The primary objective of theexperiment was to understand ionic testing and it is with confidencethat I can comfortably report that the expectations of the experimentwere met. One of the most fulfilling part of the experiment is toobserve the chemistry theory and the results which are only talkedand discussed theoretically. One area that needs a slight improvementis the opening of the chemicals to reduce the chances ofcontamination hence jeopardize the results. Sterilization of theutensils used in the opening of the chemicals would be a great stepin ensuring that the chemicals are not contaminated.
Please note that questions1-6 were adapted from the “Anions, Cations, and Ionic Reactions”LabPaq Lab manual (Hands-On Labs Version 42-0304-82-00-01, 2015)
What was the identity of the anion in Unknown # 103? Explain how you used the observations recorded in Data Table 1 to reach this conclusion.
Unknown #103 was carbonate.This is because the substance had similar chemical properties dreacted the same way as carbonate would react. It was clear that thesolution with AgNO3 formed a cloud white liquid which formed bubbleswith the addition of HCL.
2. What was the identity ofthe anion in Unknown #104? Explain how you used the observationsrecorded in Data Table 1 to reach this conclusion.
#104 was chloride. This isbecause there was no change when HCL was added and it depictedsimilar chemical composition and reactions as chloride would.Additionally, it formed a clear solution with amber sedimentationwhen added to AgNO3.
3. Write the chemicalequation for ionic reaction between Na2S and AgNO3-
This is a double replacementreaction that is balanced as follows:
4. Write the chemicalequation for ionic reaction between Na Br and AgNO3-
This is also a doublereplacement reaction that is balanced as follows:
5. What was the identity ofthe cation in Unknown #105? Explain how you used the observationsrecorded in Data Table 1 to reach this conclusion.
Unknown #105 was identified ascopper. Table 1 was used to identify the carbonate in the chemical.When a carbonate is combined with AgNO3, it forms a white clearsedimentation and the solution bubbles when HCL is added. Thesolution was identified as CuCO3.
6. If you were asked toconfirm the identity of an unknown chemical as lithium sulfide(li2S), describe the tests that you would use to confirm theidentity. Use your results in both Exercise 1 and Exercise 2 todescribe the observations in both the cation and anion tests thatwould allow the unknown to be confirmed as lithium sulfide.
In order to identify theunknown chemical, it is essential to use the two experiments. Tostart with, the cation flame test would be used to produce the darkred color flame. Adding the unknown chemical in form of powder towater would enable me carry out the anion test. Sulfide shouldproduce a clear amber color solution with sedimentation when combinedwith AgNO3. Addition of HCL would bring no change. This wouldindicate the presence of sulfide and therefore the unknown chemicalwould be lithium sulfide.
7. Have you ever noticedthe soapy ring that forms around a dirty tub? This is the product ofhard water containing Ca+2 and Mg+2 ions reacting withsoap. This soapy scum could also accumulate on our clothes if itwasn’t for detergents specifically designed to remove it. The mainchemical used to remove these ions is sodium carbonate (a chemicalused in this lab). Sodium carbonate is soluble while calciumcarbonate and magnesium carbonate are not. Suppose the water in youhome has a typical concentration of 3.6 x10-3 M Ca+2 and1.0x10-3 M Mg+2.  If your washing machine used 20.1 gallonsof water how many grams of sodium carbonate are needed to completelyprecipitate all of the calcium and magnesium ions?
20.1 gallons x 3.785 litersper gallon = 76 liters water
Moles Ca++ = 3.6×10-3 x 76liters =0.27 moles Ca++
Moles Mg++ = 1.0 x 10-3 molarx 76 liters = 0.076 moles Mg++
For each mole of Ca++ combineswith 1 mole of CO3. Each mole of Mg++ combines with 1 mole of CO3.Adding the moles of Ca++ and Mg++ we get 0.35 moles which willcombine with the CO3 ion. Therefore we will need 0.35 moles of CO3which is found in 0.35 moles of Na2CO3. This will weigh 0.35 moles x110 gramps per mole to get 37 grams Na2CO3
8. In Exercise 2 each ofthe chemicals produced a different color in the flame tests. If achemical produced a purple flame with a wavelength of 430 nm,calculate the energy associated with this wavelength. Express youranswer in J/photon.
(6.626 x 10-34)( 3 x 108) 4.3x 10-7=3 x 10-8 J/photon
9. If the energy associatedwith a wavelength of light is 1.71 x 105 J/mole what is thewavelength of that light (in nm)? What color is this light?
The light is a Red color andthe wavelength of the light is 7.00 x 102 nm
Krueger, J. H. (2010). Cationand anion chemistry.Tarrytown-on-Hudson, N.Y: Bogden & Quigley.