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LAB REPORT #2 / COURSE Group # - Surname 1, Surname 2, Surname 3, Surname 4 Experiment No. 2 PURIFICATION BY SUBLIMATION Sublimation is a change of state from the solid phase of matter directly into the gaseous state. Using it as a means of purification requires the knowledge of the effective differences in the characteristics of the substances present in the mixture from where the desired substance is to be separated. Pure salicylic acid sublimes upon heating leaving behind the impurities that may have contaminated it. In this experiment, the inorganic compound, sodium sulfate serves to facilitate the sublimation of salicylic acid and at the same time, preventing the impurities from volatilizing. OBJECTIVES: After the experiment, the learner will acquire knowledge to: 1. Separate/purify a substance by means of sublimation. EQUIPMENT AND MATERIALS: 1. Evaporating dish 2. Filter paper 3. Heating set-up 4. Wire gauze 5. Crucible tongs 6. Stirring rod 7. Spatula 8. Weighing balance 9. Funnel 10. Salicylic acid and sodium sulfate PROCEDURE: 1. Obtain a clean and dry evaporating dish and place 0.5 g of salicylic acid. Add 0.1 g of Na2SO4 and mix thoroughly. 2. Cover the dish with filter paper and fold-in the sides tightly against the sides of the dish so that it will not catch fire when the set-up is heated. 3. Make tiny holes at the center of the filter paper covering an area about the size of a 25-centavo coin. Obtain a glass funnel and plug its stem with cotton. Determine it weight and invert it on the perforated filter paper covering the evaporating dish. Make sure that the holes are covered totally by the funnel. 4. Heat the set-up with a very low flame to sublimate the salicylic acid until no more fumes is noted. Note down your observations. Let the set-up cool. 5. Weigh the funnel together with the crystals taking care that no crystals are lost. 6. Place the crystals in a dry, sealed test tube for future use. REPORT SHEET EXPERIMENT NO. 2: PURIFICATION BY SUBLIMATION DATA A. Sublimation: 1. Weigh of Na2SO4 2. Weight of salicylic acid 3. Weight of funnel 4. Weight of funnel + sublimate 5. Weight of sublimate (4 - 3) 6. Percent recovery % 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑦 = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑢𝑏𝑙𝑖𝑚𝑎𝑡𝑒 × 100% 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑙𝑖𝑐𝑦𝑙𝑖𝑐 𝑎𝑐𝑖𝑑 + 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑁𝑎2 𝑆𝑂4 GENERALIZATION/CONCLUSION: QUESTIONS: 1. What is the function of Na2SO4 in the sublimation of salicylic acid? 2. What happens with the salicylic acid when heated? 3. What happens to the gas collected in the inverted funnel? 4. What cooling system is applied in the crystallization of sublimate? 5. What is the advantage of using a cold funnel over that of a warm one as a catchment system in the sublimation process? 6. What is the purpose of plugging the stem of the funnel?