CH 105L Exp. 3 Post Lab

CH 105L Exp. 3 Post Lab - Skidmore College Name: Aamani...

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Name: Aamani Chava Date: September 27, 2007 CH 105L / Section # 002 Instructor: Prof. McClaun Directions : Type in answers below each question, using complete sentences. Adjust spacing as needed. Use 1.5 spacing in your answers. Avoid first person, and use passive voice. (100 points total) 1. In approximately three paragraphs, describe the procedure you followed in enough detail so that another student could reproduce what was done. Include and explain the following separation techniques as part of your answer: decantation, extraction, and sublimation. (15 points) Before beginning the lab, it is necessary to obtain all the equipment and clean it thoroughly. First, a clean, dry small evaporating dish must be weighed (to the nearest 0.01g-use uncertainties and record) and pour all of the unknown mixture into the dish and weighed again and the results must be recorded. After setting up the ring and ring-stand assembly, the evaporating dish with the mixture must be placed on the stand in the hood. In the hood, a Bunsen burner must be lit under the dish and allow the dish to heat until the flames from the mixture are no longer white. The dish must then cool down to room temperature and the mass should be recorded. The following procedure where the mixture is being heated is known as sublimation. Sublimation is the process where a solid transforms directly into a gas, without passing the liquid state. One of the components in the unknown mixture (ammonium chloride) is sublimated from the mixture so the mass can be recorded. After weighing the cool mixture, 25mL of water must be added to the mixture in the evaporating dish. The water must be stirred into the mixture for a few minutes for more accurate results. Another evaporating dish (large one) and watch glass (large) must be weighed and the mass must be recorded of both of the items. Now, the water in the evaporating dish with the mixture must be poured in the large, clean evaporating dish without the mixture in it. 10 mL of water must be added to the SMALL evaporating dish with the original mixture and stirred for a few minutes. The water must then be decanted into the large evaporating dish without any of the solid getting in. Another 10 mL of water must be added to the original small evaporating dish with the mixture and stirred again. This water must also then be poured into the large evaporating dish without any of the solid. The process of adding water to the mixture is known as extraction where a substance is separated from a mixture by adding another substance to it. In
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CH 105L Exp. 3 Post Lab - Skidmore College Name: Aamani...

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