Final Lab Report: Identifying Unknown Substance PDF

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Finding the Unknown

Identifying Properties of an Unknown Compound to Determine the Substance 

Michigan State University 22 March, 2018 CEM 161 Section 11   

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Introduction In one of the teaching labs at Michigan State University, an unknown white substance was found. In order to avoid a potentially dangerous chemical reaction, the unknown compound must be tested for its chemical and physical properties. This lab group is responsible for the safe disposal of this compound and the best way to do so without any problems.1 The unknown substance was narrowed down into being 1 of 15 chemicals. With only using 5 grams of this unknown substance and performing certain test they were able to eliminate certain chemicals off the list based off the results found. This process was continued until there is only 1 chemical left for the unknown to be. Below is the list of possible substances the unknown compound could have been.5 Table 1: Possible Compounds NaCl

KCl

Na2SO4

CaCl2

MgSO4

Na2CO3

K2SO4

KNO3

Ca(NO3)2

(NH4)2CO3

NH4Cl

(NH4)2SO4

CaCO3

MgCO3

CH3CO2Na

Some of these test were as follows; Solubility test, flame test, Nitrate test, determining what ions were present within the compound and comparing certain physical properties of the substance.1 Once the results from these test were found, they were compared to the results of those which were on the list of the known compounds. In doing this, they crossed off compounds which did not reveal the same results in the experiment as our unknown compound.

Experimental Procedures: In order to completely determine the compound they had to perform multiple test and determine its results. Before starting any experiment they first measured out 0.5 grams of the unknown

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substance by using the scale. Putting the cup on the scale, zeroing the scale out, then adding the correct amount of unknown substance until the scale reached 0.5 grams. Then the first experiment completed was the solubility test. This was done by adding 0.5 grams of the unknown solution into 10 mL of diluted water. Once the substance was added they began to lightly stir the mixture in order to speed up and help the reaction. After this experiment, they once again measured out 0.5 grams of the unknown substance by using the scale. The next experiment completed was the flame test. This was done by putting small particles of the unknown compound on a wooden stick. The wooden stick was then placed correctly on the flame from the bunsen burner. The color of the flame was observed while the unknown compound began to burn. This observation was recorded and compared to the known substances in the list. After these test were completed they moved onto identifying which atoms were in the unknown substances by doing a various amount of test. First the Halide test, they mixed 0.5 grams of our unknown substance and dissolved it in 10 mL of water. Then, they added 1 M of HNO3 and 1 M of AgNO3 all in 1 mL of the unknown solution dissolved in water. Then observed  the results of this mixture. To continue testing other reactions they once again got 0.5 grams of the unknown solution and added it to 10 mL of distilled water until dissolved. The next mixture, the Sulfate test, was 0.1 M of BaCl2 and 3M of HCl added to 1 mL of the unknown solution dissolved in water. After this new solution was made, they recorded any notable observations. Finally, for one of the last test they once again got 0.5 grams of the unknown solution and added it to 10 mL of water until completely dissolved. The last combination of elements we mixed 1M of CO3 added to 1 mL of the unknown solution dissolved in water. The observations from this mixture were then recorded. Once these were all completed, the team made an educated estimation on what our unknown compound was. From there, they tested the predicted compound in all the same experiments listed. Lastly, they took the results from both compounds and compared their results in order to see if they matched up.

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Results: When the substance was tested on its solubility it was found to completely dissolve in water right after adding it. At first, it was thought they may have to stir the compound in order for it to dissolve but it was just because we only added very large pieces of our compound. Once the unknown compound was burned in the flame test it produced a very deep red or dark orange color.1 This test was continued multiple times and every time produced the same dark red/orange color when burned. The Halide test with 1 M HNO3 and 1 M AgNO3 all in 10 mL of water until  it was a fully dissolved mixture mixed with the 11 mL substance of dissolved 0.5 grams of unknown with 10 mL of distilled water. It was found that there was no reaction or observations to conclude.2 The sulfate test they mixed was 0.1M of BaCl2 and 3 M of HCl added to 1 mL of dissolved unknown compound it was found that there was no reaction made.1 However, in the final mixture involving 1M CO3 added to 1 mL of the substance of dissolved unknown compound in water it was found that there was a white solid compound which floated on top when we added these two mixtures together.2 They found all these same results for the known predicted substance when we used it in all of the same experiments. Table below shows our results.3 Table 2: Data Collection Solubility: Flame Test:

Reactivity with Other Substances:

Found Dark Red/ Orange Dark Orange/Red = Must All parts dissolved (besides color was burned

be Ca2+ or Na

large chucks) Ruled Soluble in water

Observations of Mixtures: Cl + HNO3 + AgNO3  =  NOTHING No reaction CO3 + HCl = NOTHING No reaction Ca2+ + CO3 = WHITE SOLID

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 Discussion: From the very first solubility test they wanted to be able to eliminate certain compound from the list that were not soluble. Once the substance dissolved we knew that the unknown substance could not be anything that was not soluble in water. By how easily the substance dissolved in water we knew we must have had to have some sort of ion. For the flame test they knew that when certain elements were put under the flame and burned they would produce a certain color. 1 When the substance was burned and we found the dark red/orange color we were able to narrow down which element we had to either Calcium or Sodium. Again, they were only able to determine that it had to be one of these two elements based of given information on the color different elements produce when burned. For the Halide experiment which is adding the 0.5 grams of the unknown substance in 10 mL of distilled water and letting it dissolve. Mixing that with 1 M of HNO3 and 1 M of AgNO3 all in 1 mL of the solution with the unknown compound  and water. They found that there was no observations to conclude. If our unknown substance had Chlorine present, it would have reacted and resulted in a white solid floating at the top. When 2 Chlorine reacts with  HNO  white solid is produced. Therefore, since nothing was 3 and AgNO3 a 

produced we can show that our unknown substance did not have the element of Chlorine in it. The second test we did which again included 0.5 grams of the unknown dissolved in 10 mL of distilled water. Combined with a mixture of 0.1 M of BaCL2 and 3M of HCl added to 1 mL of original dissolved 0.5 grams of unknown compound again there was no observations or reaction when these 2 combined with each other. Normally, when BaCl2 and HCl are combined and mix  with SO4 there is a white solid produced.2 Therefore, because nothing was produced they were able to eliminate all substances which contained SO4 because of the lack of reaction. This left them with the last reaction of 0.5 grams of the unknown substance dissolved in 10 mL of distilled water. Which was mixed with 1M CO3 added to 1 mL of the dissolved unknown substance (in water). When this occurred they found that there was a white substance that was 4

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produced at the top of the mixture. Under normal conditions CO3 will react with C  a2+ and form a  white solid. 3 Therefore, they knew that our compound had to include the element C  a2+ in it

because of the reaction that was produced. Based off all of these things we were able to narrow down what our unknown substance was and eliminate substances that it was not. They did this by looking at Table 1 and comparing our results form our experiment in Table 2 to each compound.

Conclusion Overall, the unknown white compound was eventually identified enough to find the correct way to dispose of it. The several test we performed which were the solubility, flame test, Halide test, and Sulfate test all helped reveal the properties of this unknown compound. Not only that, but also they helped show what other elements could be found within the compound. Through these test they were able to conclude that this unknown compound includes Calcium and Nitrate within it and eliminating everything else that did not have these compounds. Therefore, the unknown substance is Calcium. Nitrate Ca(NO3)2. The best way to avoid any harmful situations during disposal is to follow government regulations regarding Calcium Nitrate Ca(NO3)2.4

References: Lab Partners: Junnuo Yu, Paul Han, and Alannah Brown 1

Dealing With Unknowns https://mynotebook.labarchives.com/ (accessed February 15th 2018)

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Effect of CO3 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3329419/ (accessed February 15th 2018)

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Individual Data Collection https://mynotebook.labarchives.com/ (accessed

February 15th 2018)

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MSDS Calcium Nitrate http://www.sciencelab.com/msds.php?msdsId=9927479 (accessed February 15th 2018)

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Scenario and Background https://mynotebook.labarchives.com/ (accessed February 15th 2018)

* All lab materials were provided by The Michigan State Department of Chemistry

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