Chem Lab #2 - Identifying Compounds Lab Partners Alexandra...

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Identifying Compounds September 18, 2008 Lab Partners: Alexandra Cross Jarrod Harbour Angel Viloria TA: Josemar Castillo
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Introduction: Oftentimes, chemists will encounter a problem where they need to figure out the identity of an unknown substance or several substances. In this case, qualitative analysis is used to figure out which elements are present in the given chemical material. Qualitative analysis deals with data in words, unlike quantitative analysis which deals with data from numbers and measurements. This is made possible through a series of reaction tests using the double displacement reaction. Once the equations are correctly formulated and balanced, the solubility table is used to determine which ions will be soluble and which will form a precipitate. The solubility table presents solubility rules of atoms and compounds that are used to determine the precipitate. There are specific clues that determine whether a chemical reaction has occurred or not. For example, any color change, gas formation, production of odor, or the formation of a insoluble solid called a precipitate is proof of a chemical reaction between the two substances. If the substance is an acid it will dissociate in liquid to form H + ions and if it is a base it will form OH- ions. Testing the unknown liquids to see if it is an acid, base, or neutral substance is the first step, which will be explained further in the procedures. By predicting the reactions through working out balanced chemical equations, and then actually performing the tests it is possible to piece together the information and figure out which substances are in which bottles. Materials and Procedures : The materials presented were: Litmus paper
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Spot plate Droppers Thermometer The first step is to determine which chemicals are acids, which are bases, and which are neutral substances. Using the droppers, a few drops of each substance were put on the litmus paper using a dropper. If the blue litmus paper turns red it is an acid and if the red litmus paper turns blue it is a base.
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