Lab #2: Separation of the Components of a Mixture Pre Lab Questions 1. The distinguishing factor between a mixture and an impure substance is that an impure substance is a type of mixture in which the amount of one of the substances in the mixture far exceeds the amounts of the other substances in the mixture. A mixture is a general term for a substance in which each of the components of the mixture retains its chemical integrity. A mixture can be separated into its components by physical means. Thus, an impure substance is specific way to classify a mixture. 2. Sublimation is the process in which a solid passes directly to the gaseous state and back to the solid state without the appearance of the liquid state. However, not all substances possess the ability to be sublimed. 3. Decantation is the process of separating a liquid from a solid (sediment) by gently pouring the liquid from the solid so as not to disturb the solid, whereas filtration is the process of separating a solid from a liquid by means of a porous substance (a filter) which allows the liquid to pass through but not the solid. These processes differ because in decantation, one must take care that the solid does not come out with the liquid. In filtration, the porous substance ensures that the solid will remain in the container, and that only the liquid will pass through the porous material. The process of decantation should be faster, but it can allow some of the solid to escape with the liquid. Even though the process of filtration is slower, it usually allows for more accuracy, because less solid comes out with the liquid. 4. One never weighs a hot object because an increased temperature can cause variations in the mass of an object. Convection currents result from hot objects, and these convection currents can cause differences in the object’s mass that can be detected by the balance. Also, handling hot objects can be dangerous, and a hot object can damage an expensive, precise balance. 5. This experiment illustrates the principle of conservation of matter in two ways. The process of sublimation illustrates conservation of matter because objects pass from the solid state to the gaseous state and then back to the solid state. Even though the matter, NH4Cl in this lab, changed states, it was neither created nor destroyed; it simply changed forms. The process of extraction also illustrates the principle of conservation of matter. In this lab, the mixture of NaCl and SiO2 was separated when distilled water was added to the mixture. The solubility of NaCl in the water and the insolubility of SiO2 allowed the separation of the NaCl and SiO2. After separating these two components through decantation, the NaCl was changed to its solid state by evaporating the water. In this process, the NaCl changed states by physical means, but it was not chemically changed in any way. The fact that these components of the mixture were separated by physical means and changed states, yet no substances were created or destroyed, exemplifies the principle of conservation of matter. 6. Total mass of mixture= 2.10 g (SiO2) + 1.38 g (cellulose) + 6.52 g (calcium carbonate) = 10.00 g % Component= (mass component in grams x 100) / (mass sample in grams) % SiO2= (2.10 g x 100) / (10.00 g) = 210 g / 10.00 g= 21.0% The percentage of SiO2 in this mixture is 21.0%. 7. You could separate a mixture of zinc chloride and cyclohexane using the process of filtration. Zinc chloride in insoluble in cyclohexane, so the solid zinc chloride can easily be separated from the liquid cyclohexane. By using filtration and pouring the mixture through some type of porous material, the liquid cyclohexane would pass over the porous material into a different container. However, the solid zinc chloride would not pass through the porous material. Thus, filtration would separate the mixture of zinc chloride and cyclohexane. 8. You could separate zinc chloride from SiO2 through the processes of extraction and decantation. Zinc chloride and SiO2 are both solids. Zinc chloride is soluble in water, but SiO2 is insoluble in water. By adding water to the mixture, the zinc chloride dissolves, leaving behind the SiO2. By decanting the liquid (containing the dissolved zinc chloride) from the solid SiO2, you will have separated these two components. By heating the solution containing water and the dissolved zinc chloride, the water will evaporate, leaving behind the zinc chloride. Thus, by these processes, zinc chloride and SiO2 can be separated. 9. The student’s calculations of NH4Cl (15%), NaCl (20%), and SiO2 (75%) differ greatly from the average calculations of NH4Cl (10%), NaCl (40%), and SiO2 (50%). Assuming her calculations are correct, there are a number of things she could have done incorrectly. She most likely performed the decantation incorrectly. Her experiment contains far less NaCl than the average NaCl found in this experiment. Most likely, she did not decant enough NaCl out of her solution of NaCl and SiO2. This mistake would have resulted in a lower percentage of NaCl but a higher percentage of SiO2, because some of the NaCl would have remained with the SiO2. Furthermore, she could have accidentally dropped or spilled portions of her mixture, and these errors could have lead to problems regarding the accuracy of her experiment. These potential problems show that although her calculations may have been correct, she did her experiment incorrectly. 10. The NaCl is extracted with water three times as opposed to only once to improve the accuracy of the experiment. Decantation is not always effective in entirely separating the soluble NaCl from the insoluble solid SiO2, thus it is important to decant multiple times to increase accuracy. When extracting the NaCl with water, some of the NaCl may not get extracted the first or second times. By extracting the NaCl with water three times, one ensures that almost all of the NaCl is successfully extracted with the water. Purpose In this lab, a mixture of NH4Cl, NaCl, and SiO2 will be separated into its three components in order to demonstrate the properties of mixtures and their ability to be separated by physical means. Reference Nelson, John H. and Kemp, Kenneth C. Laboratory Experiments to accompany Chemistry: The Central Science, 9th ed. Upper Saddle River, NJ: Pearson Education, Inc., 2003. Balanced Chemical Reactions Chemical reactions were not performed in this lab. Instead, the components of the mixture were separated by physical means. Hazards and Safety Issues In this lab, several hazards were present, so certain safety precautions had to be taken. Hair had to be tied back and away from one’s face, and any loose clothing had to be secured due to the flammability hazard of the Bunsen burner. Additionally, one had to wash their hands after completing this lab. The components in this lab, NH4Cl, SiO2, and NaCl, could have potentially been dangerous if they came into contact with one’s eyes, nose, mouth, food, or any other objects. Moreover, goggles had to be worn in order to prevent any chemicals or fumes from irritating one’s eyes due to spattering or boiling of heated solutions. Closed-toe shoes were worn due to the fact that glassware was being handled in the lab. In the instance that the glassware was dropped, it could have shattered and caused severe injuries. Furthermore, in this lab, an improvised fume hood, consisting of an aspirator, cork, funnel, and test tubing, was used for the sublimation of the NH4Cl from the mixture. This improvised fume hood ensured that the NH4Cl fumes were not released directly into the air and could not cause any possible issues. Materials The following materials were used in this lab: Glassware: Watch glass, 50- or 100-mL graduated cylinder, glass stirring rods, improvised fume hood (funnel, aspirator) Hardware: Triple beam balance, Bunsen burner and hose, crucible tongs, beaker tongs, 2 evaporating dishes, 2 wire gauze, 2 ring stands, 2 iron rings, improvised fume hood (cork, test tubing) Reagents: Sodium chloride (NaCl), Ammonium chloride (NH4Cl), Silicon dioxide (SiO2), distilled water Procedure Initial Steps and Sublimation of NH4Cl: 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 Extraction and Decantation of NaCl 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 Calculation of SiO2 If the SiO2 is still wet: 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 cool Weigh it and calculate the mass of the SiO2 OR If the SiO2 has dried out naturally: Weigh the evaporating dish with the SiO2 Calculate the mass of the SiO2 Data/Observation Tables Sample C Initial Steps and Sublimation of NH4Cl: Mass of evaporating dish and original sample 94.721 g Mass of evaporating dish 92.344 g Mass of evaporating dish after subliming 94.441 g NH4Cl Extraction of NaCl: Mass of evaporating dish, watch glass, and 46.919 g NaCl Mass of evaporating dish and watch glass 46.028 g Measurement of SiO2: Mass of evaporating dish and SiO2 93.512 g Mass of evaporating dish 92.329 g Observations: 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. Some SiO2 particles would have came out of the first evaporating dish into the second evaporating dish with the NaCl solution if too much NaCl solution was decanted. In order to separate the two components as accurately as possible, distilled water was added to the first evaporating dish and the NaCl solution was decanted three separate times. Twenty-four hours passed between the time when the NaCl solution was decanted and when the water was to be evaporated from the NaCl solution, so some of the water in the solution had already evaporated. While the NaCl solution was heated to evaporate the water, the water quickly began to boil and spatter, so the watch glass was placed over the evaporating dish. As the water evaporated, the solid NaCl attached to various parts of the evaporating dish and watch glass. The Bunsen burner was not needed to remove any water from the SiO2, because the water had evaporated after being left out for 48 hours. The results indicated that the original sample contained a higher percentage of SiO2 than of the other components. Clean Up Clean up is necessary in labs for the safety of students and the instructor. It is important to dispose of chemicals in certain, predetermined ways, because particular chemicals are very hazardous. In this lab, the NH4Cl was disposed of by being evaporated, and the aspirator ensured that it was ultimately washed down the sink. The SiO2 was placed in a container at the front of the room, and would later be disposed of properly. After the evaporating dish containing the NaCl was weighed, it was cleaned out using water, and the NaCl was disposed of down the sink. As general housekeeping practices, the objects that were heated during the lab were left out on the table so they could cool down, while the unheated apparatuses were put away in the drawers and cupboards for the other people who were working on the lab. The objects were cleaned using water before being put away. The counter top was also washed with water. This was to insure that future labs performed were accurate. Also, during the lab, the equipment and solutions of other lab groups were left alone and not interfered with. Calculations and Analysis of Data Initial Steps and Sublimation of NH4Cl: (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ 𝑎𝑛𝑑 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) − (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ) = (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) 94.721𝑔 − 92.344𝑔 = 2.377𝑔 (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ 𝑎𝑛𝑑 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) − (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ 𝑎𝑓𝑡𝑒𝑟 𝑠𝑢𝑏𝑙𝑖𝑚𝑖𝑛𝑔 𝑁𝐻4𝐶𝑙) = (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝐻4𝐶𝑙) 94.721𝑔 − 94.441𝑔 = 0.280𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝐻4𝐶𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑁𝐻4𝐶𝑙) 0.280𝑔 × 100 = 11.8% 2.377𝑔 (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) × (𝑎𝑐𝑡𝑢𝑎𝑙 𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑁𝐻4𝐶𝑙) = (𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒) 2.377𝑔 × 12% = 2.377 𝑔 × 0.12 = 0.2852 𝑔 |𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑣𝑎𝑙𝑢𝑒−𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒| 𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑒𝑟𝑟𝑜𝑟) |0.280𝑔 − 0.2852𝑔| × 100 = 1.82% 0.2852𝑔 Extraction and Decantation of NaCl: (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ, 𝑤𝑎𝑡𝑐ℎ 𝑔𝑙𝑎𝑠𝑠, 𝑎𝑛𝑑 𝑁𝑎𝐶𝑙) − (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ 𝑎𝑛𝑑 𝑤𝑎𝑡𝑐ℎ 𝑔𝑙𝑎𝑠𝑠) = (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐶𝑙) 46.919𝑔 − 46.028𝑔 = 0.891𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐶𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑁𝑎𝐶𝑙) 0.891𝑔 × 100 = 37.5% 2.377𝑔 (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) × (𝑎𝑐𝑡𝑢𝑎𝑙 𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑁𝑎𝐶𝑙) = (𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒) 2.377𝑔 × 38% = 2.377 𝑔 × 0.38 = 0.9033𝑔 |𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑣𝑎𝑙𝑢𝑒−𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒| 𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑒𝑟𝑟𝑜𝑟) |0.891𝑔 − 0.9033𝑔| × 100 = 1.36% 0.9033𝑔 Calculation of SiO2 (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ 𝑎𝑛𝑑 𝑆𝑖𝑂2) − (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑛𝑔 𝑑𝑖𝑠ℎ) = (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑆𝑖𝑂2) 93.512𝑔 − 92.329𝑔 = 1.183𝑔 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑆𝑖𝑂2 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑆𝑖𝑂2) 1.183𝑔 × 100 = 49.77% 2.377𝑔 (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) × (𝑎𝑐𝑡𝑢𝑎𝑙 𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑆𝑖𝑂2) = (𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒) 2.377𝑔 × 50% = 2.377𝑔 × 0.50 = 1.189𝑔 |𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑣𝑎𝑙𝑢𝑒−𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒| 𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑒𝑟𝑟𝑜𝑟) |1.183𝑔 − 1.189𝑔| × 100 = 0.5046% 1.189𝑔 Percent Error (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝐻4𝐶𝑙) + (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐶𝑙) + (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑆𝑖𝑂2) = (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑑𝑒𝑡𝑒𝑟𝑚𝑖𝑛𝑒𝑑 (𝑁𝐻4𝐶𝑙 + 𝑁𝑎𝐶𝑙 + 𝑆𝑖𝑂2)) 0.280𝑔 + 0.891𝑔 + 1.183𝑔 = 2.354𝑔 (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒) − (𝑚𝑎𝑠𝑠 𝑜𝑓 𝑑𝑒𝑡𝑒𝑟𝑚𝑖𝑛𝑒𝑑 (𝑁𝐻4𝐶𝑙 + 𝑁𝑎𝐶𝑙 + 𝑆𝑖𝑂2)) = (𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒𝑠 𝑖𝑛 𝑡ℎ𝑒𝑠𝑒 𝑤𝑒𝑖𝑔ℎ𝑡𝑠) 2.377𝑔 − 2.354𝑔 = 0.023𝑔 𝑔 𝑚𝑎𝑡𝑡𝑒𝑟 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑔 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑠𝑎𝑚𝑝𝑙𝑒 × 100 = (𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑦 𝑜𝑓 𝑚𝑎𝑡𝑡𝑒𝑟) 2.354𝑔 2.377𝑔 |𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑣𝑎𝑙𝑢𝑒−𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒| 𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 × 100 = 99.03% × 100 = (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑒𝑟𝑟𝑜𝑟) |2.354𝑔 − 2.377𝑔| × 100 = 0.9676% 2.377𝑔 Comparison of the Masses of Each Component vs. the Actual Masses 1.4 1.183 1.2 Mass (in grams) 1 0.891 1.189 0.903 0.8 0.6 0.4 0.280 0.285 0.2 0 Ammonium Chloride (NH4Cl) Sodium Chloride (NaCl) Sand (SiO2) Measured Mass (in grams) Actual Mass (in grams) Component of the Mixture Discussion: The main concept being applied and studied in this lab was the separation of components of mixtures by physical means. A mixture is a material that is not uniform in composition, and it is a combination of two or more substances in which each substance retains its own chemical identity. Mixtures are characterized by the fact that each of the substances in the mixture retains its chemical integrity, and that mixtures are separable into these components by physical means. 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. A physical change is a change, such as a phase change, that occurs with no change in chemical composition. When measuring the different amounts of the three components of the mixture, all measurements were based on significant figures. Thus, each certain digit plus one uncertain digit was included in all measurements. The process of sublimation, in which a solid passes directly to the gaseous state and back to the solid state without the appearance of the liquid state, was used to separate the NH4Cl from the rest of the mixture. The sublimation effectively separated the NH4Cl from the rest of the mixture. The original sample contained 0.280 g of NH4Cl. In reality, the sample truly contained 0.285 g of NH4Cl. Later on, the NaCl was separated from the SiO2 because of the solubility of NaCl in water and the insolubility of SiO2 in water. Solubility is the ability of a substance to dissolve when in the presence of a certain solvent. The process of extraction, in which a substance is separated from a mixture by dissolving that substance in a suitable solvent, was used to separate the NaCl from the SiO2. The NaCl dissolved in the water, and by decantation, the process of separating a liquid from a solid by gently pouring the liquid from the solid so as not to disturb the solid, the NaCl solution was separated from the SiO2. Heating can cause substances to evaporate, which represents a change in state, so the water was evaporated from the NaCl, which left behind the solid NaCl. The amount of NaCl in the experiment was measured to be 0.891 g, but the original sample actually contained 0.903 g of NaCl. Then, the remaining component of the mixture, SiO2, was measured to be 1.183 g once it had dried out. The actual amount of SiO2 in the mixture was 1.189 g. The comparison between the measured masses of the three different substances in the mixture and the actual masses of the components proved that the substances of mixtures are able to separated, yet still retain their chemical and physical properties. After the components of the original sample were successfully separated, their masses were added together in order to determine whether their added masses equaled their original mass. The measured total of the three separate components in the mixture was 2.354 g, whereas the mass of the original sample was 2.377 g. Thus, this similar correlation between the masses proves that all three components had relatively the same masses before and after they were separated from the mixture. When the percentages of each component in the mixture were calculated and subsequently added together, the total was 99.033%. Ideally, the total percentage should have been 100%, because substances are neither created nor destroyed during these physical separation methods, according to the principle of conservation of matter. However, the total percentage is extremely close to 100%, and minor errors, such as incorrect measurements, could have caused this slight deviation from the actual total. This total proximity to 100% proves the concept that mixtures can be separated into their components by physical means, and that their components will retain their initial properties. Conclusion: Yes, the ability of the mixture of NH4Cl, NaCl, and NH4Cl 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. Sources of Lab Error: 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. On the other hand, some of the water with the dissolved NaCl may not have been decanted from the solid SiO2. Both of these potential errors would have resulted in errors in later calculations. Moreover, another potential source of error could have been an insufficient sublimation of NH4Cl. The sublimation was supposed to be terminated when the white fumes ceased to exist. However, a possible error was the misjudgment of the termination of the white fumes. It could have been perceived that there were no more white fumes, when in reality there were still more white fumes, and consequently the sublimation process could have been ended too early. This error would have resulted in a lower calculated mass of NH4Cl. Post Lab Questions: 1. No, the separation in this experiment could not have been done in a different order. This experiment needed to be performed in the order specified in this procedure. The ammonium chloride needed to first be sublimed from the mixture. Sublimation is the process in which matter changes from a solid state to a gaseous state and back to a solid state, without experiencing the liquid state. Ammonium chloride is soluble in water, so if the mixture were first extracted with water, both the ammonium chloride and the sodium chloride would dissolve in the water, leaving behind the sand. When the extract, containing the water with the dissolved ammonium chloride and sodium chloride, was heated to dryness, the ammonium chloride would not be able to be sublimed. Sublimation begins at a solid state, but when the ammonium chloride was dissolved in the water, it would not be in a solid state, so it would not sublime easily. The presence of the ammonium chloride with the sodium chloride could also prevent this solution from drying out properly. Thus, the steps in this experiment could not have been done in a different order. 2. You could separate barium sulfate, BaSO4, from NH4Cl through the process of sublimation. NH4Cl is able to be sublimed, whereas BaSO4 is not. Thus, by subliming the NH4Cl out of the mixture, you would be left with the BaSO4. By subliming the NH4Cl from the mixture and allowing it to return to the solid state apart from the original mixture, you could separate the components of this mixture. 3. You could separate zinc chloride, ZnCl2, from zinc sulfide, ZnS, by the processes of extraction and decantation. First, you would use extraction and add water to the mixture. By adding water, the soluble ZnCl2 would dissolve, leaving behind the solid ZnS. To separate these components, you could decant the water, containing the dissolved ZnCl2, from the solid ZnS. Then, you could heat the ZnCl2 solution to evaporate the water, leaving behind the ZnCl2. Thus, the processes of extraction and decantation could separate the components of this mixture. 4. You could separate tellurium dioxide, TeO2, from SiO2 through the processes of extraction and decantation. SiO2 is soluble in hydrofluoric acid, whereas TeO2 is insoluble in hydrofluoric acid. Thus, by adding hydrofluoric acid to your mixture, the SiO2 will dissolve, leaving behind the TeO2. Then, separate these components through decantation, by separating the hydrofluoric acid (containing the dissolved SiO2) from the solid TeO2. After allowing the SiO2 solution to dry and evaporate, the hydrofluoric acid will evaporate, leaving behind the SiO2. You will have successfully separated the components of the mixture. 5. You could separate naphthalene and potassium bromide by the process of sublimation. By heating the mixture, the naphthalene will be sublimed from a solid state to a gaseous state and back to a solid state, apart from the potassium bromide. The potassium bromide will not sublime, so it will be left behind when the naphthalene undergoes sublimation. By this process, you can separate these two substances.