Unknown White Compound

Unknown White Compound Identifying the chemical makeup of an unknown white substance by conducting a series of tests including a flame test, conductivity test, ion test, and a pH test March 28, 2022 Spring 2022 Abstract The purpose of this experiment was to identify an unknown white compound through a series of tests and later, synthesize the given compound once identified and compare the synthesized compound versus the known compound. In order to identify the unknown white compound, a series of tests were performed including a flame test, an ion test, a conductivity test, and a pH test. The flame test confirmed that the compound consisted of magnesium due to the lack of color it produced during the reaction while the ion test confirmed that there was a presence of chlorine in the compound. It was apparent that the compound was magnesium chloride however, it was not confirmed. The conductivity test and pH test compared a known magnesium chloride compound to the unknown white compound which resulted in both the pH and conductivity being identical. In an attempt to synthesize magnesium chloride, the reaction was not successful, which resulted in putting a halt to the experiment. Introduction This experiment is relative to real-world applications in the sense that individuals can identify a compound to ensure that it is safe for biological beings or if it is hazardous. Additionally, this experiment can be used to identify or discover unknown compounds. According to Basem Kanawat, a research analytical chemist, a series of tests was used in order to identify an unknown class of metalorganic compounds found in meteorites (Kanawat, 2017). Kanawat conducted solubility tests on all of the unknown compounds as well as electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry in an attempt to determine the chemical makeup of these compounds.1 Although the tests conducted in the experiment were not as complex, the scientific process was similar and the experimental purpose was identical. In addition to Kanawat's research, the process of identifying unknown compounds is widely used in forensic sciences. According to the National Forensic Science Technology Center, or the NFCTC, chemistry is used to identify illegal substances within the criminal justice system. Oftentimes, illegal substances are masked with other substances in order to be transported without detection. Forensic scientists use compound identification strategies in order to identify substances.2 Lastly, the identification of unknown compounds is used for health benefits. Milk has been identified as a staple in adequate growth and development in adolescents but why is milk more nutritious than water or fruit juices? According to the Nation Institute of Standards and Technology, scientists have conducted identification experiments to pinpoint the exact nutrients that give milk its infamous properties.3 The experimental purpose of the experiment was to identify an unknown white compound through a series of four tests. The tests that were performed were a flame test, an ion test, a conductivity test, and a pH test. With a list provided, the compound could have been one of fifteen compounds. Due to the appearance of the compound alone, it was impossible to confidently create a hypothesis of what the compound would be but if the experiments were conducted correctly, then the compound would be identified. The context of the report includes the procedures followed during the experiment, the results and identity of the unknown white compound, and the overall conclusion of the experiment. Experimental The first experiment conducted was the flame test. Due to its lack of precision in identifying the compound, this experiment decreased the number of possible compounds. After gathering the required materials, connect one end of the rubber wire to the gas supply and the other end to the Bunsen burner. In addition to these materials, fill one beaker with 50mL of deionized water and one beaker with 10mL of 1M HCl. After concocting a slurry by mixing 0.1g of the solid, unknown white compound and 2-3 drops of deionized water in a test tube, 0.1g of the unknown white compound was measured on a scale. Once the substance had been measured, a funnel was used to carefully transfer the unknown white compound into a test tube. Using a pipet, 2-3 drops of deionized water were added into the test tube with the substance and swirled to combine. This process was repeated with the remaining compounds that were chosen to test with. Originally, there were 5 different slurries created in addition to the unknown white compound slurry. Once all slurries were created, the gas unit was turned on and the Bunsen burner was lit using a match. The oxygen dial was turned until the flame was completely blue. Making the flame completely blue ensures that the color of the flame will not affect the results. After cleaning the nichrome wire by dipping it in the HCl and then into the deionized water, the nichrome wire was wiped with a paper towel and placed over the flame. The production of no color change ensures that the nichrome wire is clean. If there was a color change, there was still substance present and the cleaning steps were repeated until the flame produced no color change. Once the nichrome wire was completely clean, the wire was left for 30 seconds to cool. Once cooled, the looped end of the nichrome wire was dipped into the unknown white compound slurry and placed in the flame. The color change was recorded. The color change of the flame reacted in the same sense as a compound containing magnesium. The flame test was then conducted for the compound MgCl2 to confirm the hypothesis that our compound contained magnesium. Using 0.1g of MgCl2 and 2-3 drops of deionized water, the steps taken to complete the flame test with the unknown white compound were used to complete the flame test with MgCl2. The flame also did not produce any color which confirmed the hypothesis. Once the results confirmed the hypothesis, there was no need to further the experiment with the rest of the slurries created. Record the color change and dispose of the slurries into the correct disposal containers. Neutralize the HCl before disposing. In addition to the flame test, an ion test was conducted to determine the second element in the compound. In order to perform the carbonate ion test, 1mL of 6M HCl was measured and poured into a graduated cylinder. 0.5g of the unknown white compound and 1mL of deionized water was combined in a test tube and swirled to combine. The 6M HCl was added into the test tube with the unknown white compound solution and observed for bubbling and fizzing. The reaction results were recorded in a data table. This process was repeated with 0.5g of MgCl2 and MgSO4 and recorded the results. The compounds that did not have the same reaction were eliminated. With the carbonate test, an ammonium cation test was also conducted. Similarly to the carbonate test, 0.5g of the unknown white compound was measured and turned into a solution with 10mL of deionized water. This solution was added to a test tube with 1mL of 6m NaOH and swirled to combine. If ions are present, ammonium gas would have been released from the system and an unpleasant order comparable to urine or eggs would be detected by the nose. The steps were repeated with the 0.5g of MgCl2 and MgSO4 and the compounds that did not react in the same way as the unknown white compound were eliminated. Additionally, a sulfate test was conducted. 0.5g of the unknown white compound was measured and added to a test tube and 1mL of 6M HCl and 1mL of 0.1M BaCl2. The system was observed for a reaction. If sulfates were present, a precipitate would have formed. The steps were repeated with 0.5g of MgCl2 and MgSO4 and the results were compared. For even further confirmation, a halides test was performed. 0.5g of the unknown white compound was measured and added to 10mL of deionized water in order to create a solution. 1mL of that solution was added into a test tube and 1mL of 6M HNO3 and 0.1M of AgNO3 were also added into the test tube. The formation of a white precipitate indicates the presence of halide ions and sometimes acetate or sulfate ions. In addition to the other tests, a conductivity test was used. The conductivity probe was connected to the GoLink! Connector and then to the computer with the software LoggerPro installed. After the conductivity probe was connected, 0.2g of the unknown white compound was measured and placed into the beaker with 10mL of deionized water in a 10mL graduated cylinder. The contents were swirled in the beaker to combine. This solution will be a 0.2M solution of the unknown white compound. The steps were repeated with 0.2g of MgCl2 and 10mL of deionized water to create a 0.2M solution of MgCl2. Before conducting the experiment the conductivity probe was calibrated in deionized water. Place the probe into a 250mL beaker with 100mL of deionized water and run the LoggerPro software. If calibrated correctly, the value should be close to zero. Once calibrated, the experiment continued. The probe was wiped with a KimWipe to ensure that it was completely dry and free of other contaminants. The probe was placed into the 0.2M solution of the unknown white compound and the program was utilized. The conductivity value that was given was recorded in the data table. The probe was cleaned in deionized water and wiped with a KimWipe. This process was repeated one more time totalling in two trials, making sure to record each value. Making sure to clean the probe thoroughly, the procedure was repeated with a 0.2M solution of MgCl2 making sure to record each value for both trials. The values were compared to the unknown white compound and the MgCl2. The solutions were disposed of in the designated disposal containers and the probe was cleaned before returning it to its designated spot. With the other 3 tests, a pH test was used to further confirm the hypothesis. A pH probe was connected to a computer with the LoggerPro software installed. After being connected, the probe was cleaned in deionized water and was left to air dry. The pH probe was calibrated using two buffer solutions of pH 4 and 7. As the software was running, the probe was swirled in the solution to allow the values to stabilize. Once the reading was stable, the first value of the buffer solution was recorded in the “reading 1” box and kept. The probe was then removed and rinsed with deionized water and dried with a fresh Kimwipe. Once cleaned, the probe was placed in the second buffer solution and briefly swirled to allow the reading to stabilize. Once the reading was stable, the value of the buffer solution was recorded in the “reading 2” box and kept. The probe was then removed and rinsed with DI water and dried with a fresh Kimwipe. The probe was then placed into a 100 mL beaker filled with 50 mL DI water, to test if the probe system reads a pH of 7. This was then used to compare with the UWC solution. The unknown white compound solution was created by mixing 10mL of deionized water with 2.0g of the unknown white compound and swirling to combine. The probe was placed in the UWC solution and briefly swirled until the computer reading stabilized, making sure the probe was completely dipped into the solution. Once the reading was stable, the first value of the buffer solution was recorded in the “reading 1” box and kept. The probe was rinsed with DI water and dried with a fresh Kimwipe. After using the probe, pH strips were used in order to add extra certainty in the results. The strips were used by dipping the strip in the prepared unknown white compound solution already used in the pH test and the color of the strip was recorded. The strip test was repeated with MgCl2. The solutions were disposed in appropriate waste containers In order to calculate how much magnesium ribbon and HCl needed in order to synthesize 1.0g of MgCl2, the balanced equation, Mg(s) + 2 HCl(aq) → MgCl2 (aq)+ H2(g) was used. Considering that magnesium was the limiting reagent, using stoichiometry, the amount of magnesium needed in order to synthesize 1.0g of MgCl2 was about 25g of magnesium. With the consideration of experimental error, an excess of 5.0g was used totallaling in 30.0g of magnesium used. With that information, it was known that 1 mole of magnesium needed to be 2 moles of HCl. The stoichiometric calculations revealed that 3.34mL of 6M HCl was needed to synthesize 30.0g of magnesium. To synthesize 1.0g MgCl2, 30.0g of magnesium ribbon was measured. In order to speed up the reaction, scissors were used to cut the magnesium ribbon into small pieces to increase surface area. The cut pieces of magnesium ribbon were placed into a 400mL beaker and 3.34mL of 6M HCl was added into the beaker. The beaker was left to synthesize for 30+ minutes. In 5 minute intervals, the contents in the beaker were swirled to promote the reaction. Results Data Table 1: Flame Color Observed From Compounds During the Flame Test Compound Trial 1 Trial 2 Trial 3 MgCl2 No color No color No color Unknown No color No color No color Compound The results of the flame test showed that both the unknown white compound and MgCl2 did not produce any color. Due to the unknown white compound not producing any color, the hypothesis stated that the unknown compound contained magnesium as magnesium also does not produce any color in a flame test. Due to this information, the decision was made not to conduct the flame test on the other compounds listed in the experimental section since it was apparent that the first element in the compound was magnesium. Data table 2: Ion Test Reactions (Unknown White Compound) Test Conducted Result Ammonium No smell, No precipitate formed Halide No precipitate formed Sulfate No precipitate formed Carbonate No fizzing/bubbling Data Table 3: Ion Test Reactions (MgCl2) Test Conducted Result Ammonium No smell, No precipitate formed Halide No precipitate formed Sulfate No precipitate formed Carbonate No fizzing/bubbling Data Table 3: Ion Test Reactions (MgSO4) Test Conducted Result Ammonium No smell, No precipitate formed Halide Precipitate formed Sulfate No precipitate formed Carbonate No fizzing/bubbling According to the data tables above, the results of the ammonium, halide, sulfate and carbonate tests were identical with the unknown white compound and MgCl2 while MgSO4 formed a precipitate with the halide test since halide tests can sometimes identify a sulfate in a compound. The ion tests confirmed that our unknown white compound was MgCl2. Data Table 4: Conductivity Values Trial MgCl2 1 2 Average UWC 2.56E+04µS/c 2.69E+04µS/c m m 2.53E+04µS/c 2.47E+04µS/c m m 2.55E+04µS/c 2.58E+04µS/c m m The results of the conductivity test revealed that the unknown white compound’s conductivity was extremely similar to that of MgCl2 at a 2.0M solution. Due to movement and possible leftover substances the numbers fluctuated slightly, however, the values were close enough to each other where one could confidently conclude that the known white compound had the same conductivity as MgCl2. Data Table 5: pH values from pH test pH MgCl2 UWC 6.11 (defunkt as probe wasn’t Between 7 and 8 working) pH 7.85 (defunkt as probe wasn’t working) Between 7 and 8 The pH papers were matching in color when dipped in a 2.0M solution of the unknown white compound and MgCl2, the resulting color being somewhere between 7 and 8. This further confirmed that the compound is MgCl2 as the pH’s of the two solutions were the same. Both solutions had a high pH of 7 as the resulting pH paper was more green than yellow. Flame Test with Synthesized Compound Data Table Due to the lack of time and a magnesium oxide coating on the magnesium ribbon, the compound did not synthesize. What was left was an oxidized ribbon and HCl. Due to this, the experiment was unable to continue. Discussion During the flame test, an ion will produce a color change to the flame due to the rupture of covalent bonds during the reaction. A colorless flame may occur if the atoms are excited and drop down to a ground state. These types of reactions produce an immense amount of energy causing the flame to turn ultraviolet which cannot be seen by the naked eye which results in “no color change”. The unknown white compound had not produced any color change in the flame which was concluded, with further research, that the compound was composed of magnesium. The results of the flame test had narrowed down the list substantially as only 2/15 possible compounds contained magnesium. Although the flame test could narrow down the list, it could not pinpoint the exact compound. In order to do that, an ion test was conducted. Since the compound contained magnesium, the only options that the compound could potentially be were MgCl2 and MgSO4. During the halide and sulfate tests, a precipitate will form if sulfates or halides are present. By adding acid to the compound, it will react with halides or sulfates and create a precipitate. During the carbonate test, carbonate molecules are unstable so when in contact with hydrochloric acid, carbon dioxide gas is released which causes the fizzing and bubbling. In the ammonium test, pH paper is used to test the acidity or alkalinity of the solution and gas. Since ammonium is a basic gas, it will turn the moist paper blue. This is another indicator that ammonium is present. Since ammonium gas is being released from the system, the paper is held above the solution rather than placed in the solution to ensure that the paper is testing the pH of the gas that is being released rather than the solution itself. Conductivity is the measure of the ability for an electric current to pass through a solution. Conductivity is measured using a probe in Siemens. In water, ions are free to move from place to place which allows them to conduct electricity as they are not in a fixed location. Ions are then charged and attract to oppositely charged electrodes. pH can also be used to identify a compound as acidic, basic, or neutral which can determine the chemical makeup of a compound. It can also be used to compare the pH of different compounds to test similarities like how the pH test was used to compare the unknown white compound and MgCl2. MgCl2 is an ionic compound which means that it is polar and makes it soluble in water. Polar bonds are hydrophilic which means they attract water molecules which break down the bonds. During synthesis, solid magnesium ribbon is added to HCl and as H2 gas is released from the system, the remaining product remaining will be MgCl2. This type of reaction is a single replacement reaction. In order to separate each product, there was little work that needed to be done. Since all of the hydrogen gas would have been released from the system, the only remaining reactants would be magnesium and calcium. Conclusion The unknown white compound given was a granular, white substance that did not appear to have a scent. Because of the broad spectrum that the compound could be, it was impossible to identify the compound simply by its appearance. While conducting the flame test, the unknown white compound did not produce any color within the flame which revealed that the unknown white compound was composed of magnesium. When testing MgCl2, the same results were achieved as the unknown substance which confirmed the hypothesis. This left two possible compounds, MgCl2 and MgSO4. The sulfates test indicated that the unknown white compound did not have any sulfates. If sulfates were present, the mixture would have produced a precipitate when combined with 6M HCl and 0.1M BaCl2. The unknown white compound did not react with the HCl and BaCl2 which concluded that there were no sulfates. The halides test is used to reveal the presence of halides in a compound; however, it may also reveal the presence of sulfates or acetate ions. MgSO4 reacted with the halides test as it did form a precipitate while MgCl2 and the unknown white compound did not. Due to MgCl2 and the unknown white compound reacting in the same way, it was revealed that the unknown white compound was MgCl2. In order to confirm even further, a comparison of the conductivity of the unknown white compound, which was believed to be MgCl2, and the premade MgCl2. The values that were presented after the conductivity test were extremely similar to one another as MgCl2 had an average conductivity of 2.55E+04µS/cm at 0.2M and the unknown white compound had a conductivity value of 2.58E+04µS/cm at 0.2M. Lastly, a pH test was used. The colors of the pH paper when dipped in a 0.2M solution of the unknown white compound and a separate solution of 0.2M MgCl2 were the same. The pH was read to be about 7-8 since both solutions revealed a greenish-yellow color. While trying to synthesize MgCl2, the process was unsuccessful. Due to the MgO coating on the magnesium ribbon, the HCl was unable to penetrate and correctly react with the magnesium in the time allotted. If done correctly, the HCl and magnesium ribbon would have reacted and hydrogen gas would have been released from the system leaving the MgCl2 compound behind. Due to this, it was impossible to compare the synthesized MgCl2 and the premade MgCl2. A possible extension of this experiment would be using earth metals rather than white compounds. Scientists would be able to determine the identity of unknown metals by following identification procedures similarly to the experiments conducted for the unknown white compounds. A similar experimental process would be conducted to identify unknown metals found in the earth or in extraterrestrial substances.