Separation Of Substances: Sublimation, Extraction, Sub

Purpose
This experiment deals with separating substances. The objective was to become familiar with the methods of separating substances from one another using decantation, extraction, sublimation techniques.
Brief Introduction This experiment was set to teach research students different methods of separating substances from one another. Materials that are not uniform in composition are set to be impure or heterogeneous and are called mixtures. The separation of the components of mixtures is based upon the fact that each component has different physical properties. The components of mixtures are always pure substances, either compounds or elements, and each pure substance possesses a unique set of properties. Every crystal of a pure substance
melts at a specific temperature, and at a given pressure, every pure substance boils at a specific temperature. In this experiment the research student will use four methods of separation depending on differences in physical properties. These methods include: 1) decantation- involves the separation of a liquid from insoluble solid sediment by carefully pouring the liquid without disturbing the solid 2)Filtration- involves separating a liquid from a solid using a porous material 3) Extraction- involves using a solvent that selectively dissolves only a single component while the other components remain insoluble 4)Sublimation- involves the heating of a solid that passes directly into a gaseous phase without transitioning into a liquid phase.
Brief Procedure and Any Modifications
Weigh an empty evaporating dish to the nearest 0.001 g using a triple beam balance. Obtain 2-3 g of unknown substance from the instructor. Set up an improvised fume hood consisting of an aspirator, cork, test tubing, and funnel to capture the NH4Cl fumes during the sublimation process. Place the unknown substance in the evaporating dish, and then weigh it. Place the evaporating dish on wire gauze on the iron ring stand. Light the Bunsen burner and adapt it until there is a darker inner flame inside the lighter outer flame. Place the Bunsen burner underneath the improvised fume hood. Heat the evaporating dish for 15 minutes (or until the white fumes disappear). Carefully shake the evaporating dish during the sublimation process. Let the evaporation dish cool. Weigh the dish. Perform the appropriate calculations to
determine the mass of the NH4Cl. Add 25 mL of water to the substance in the evaporating dish. Stir the water and the substance together. Weigh a second evaporating dish and watch glass. Decant the water by gently pouring it out into the second evaporating dish. Add another 10mL of water to the first evaporating dish. Decant the water into the second. Repeat last two steps. There are now two evaporating dishes, one with wet sand and one with sodium chloride. Place the evaporating dish with the sodium chloride on the iron ring stand. Light the Bunsen burner until the flame has a dark blue inner flame and a lighter blue outer flame. Place the Bunsen burner underneath the improvised fume hood. Heat the solution to evaporate the water. Towards the end of the heating, cover the dish with the watch glass. When no more water will condense on the watch glass, the sodium chloride will have been dried completely. Let both the evaporating dish and the watch glass cool. Weigh the evaporating dish and calculate the mass of NaCl. If the SiO2 is still wet, then place the dish with the wet sand on the iron ring stand. Light the Bunsen burner until the flame has a darker inner flame and a lighter blue outer flame. Place the Bunsen burner underneath the improvised fume hood. First, heat the sand until the lumps of sand break up and the sand becomes dry. Heat for 10 minutes and until the sand becomes a dull red color. Let it cool. Weigh it and calculate the mass of the SiO2. If the SiO2 has dried out naturally, weigh the evaporating dish with the SiO2. Calculate the mass of the SiO2.

Results/Report Sheet (Data/Observations/Calculations/Error Analysis) and Discussion
Tongs were used to handle any evaporating dishes or watch glasses during this lab.
The oils on one’s hands could have altered the masses of this equipment due to the accurate, precise nature of the balance. During the sublimation of NH4Cl from the mixture, white fumes were produced. The improvised fume hood transported the white fumes away from the work area. In this process, the solid NH4Cl changed into a gaseous state and then later on back into a solid again. As the distilled water was added to the NaCl and SiO2 mixture, the soluble NaCl dissolved in the water, allowing these two components to be separated through decantation. The water containing the dissolved NaCl was decanted from the solid SiO2, but it was extremely difficult to remove all drops of water from the evaporating dish containing the SiO2 in order to completely separate these two components. In this lab, the starting point was a mixture of NH4Cl (Ammonium chloride), NaCl (sodium chloride), and SiO2 (sand). Each of these substances retained its own chemical identity throughout the course of this lab. NH4Cl and NaCl are ionic compounds, in which normally a metal bonds to a nonmetal, based on the charges of the ions. SiO2 is a binary molecular compound, which is a combination of two nonmetals that is named using Greek prefixes to clarify the number of each type of atom in the compound. In this lab, the components of the mixture were separated by physical means, and consequently the components underwent
physical changes. During this lab, several aspects might have caused the values to deviate from the expected values. During several stages of the experiment, figures on the balance could have been read incorrectly. An incorrect reading could have resulted in significant variations in subsequent calculations. Another possible source of lab error was the process during which the water containing the dissolved NaCl was decanted from the solid SiO2. During the three times that the decantation was performed, some of the SiO2 may have come out with the water.
Conclusion (and any References if any)
Yes, the ability of the mixture of NH4Cl, NaCl, and SiO2 to be separated into different substances by physical means supports the stated purpose and proves that mixtures can be separated into their components by physical means.