coffee cup calorimetry

# coffee cup calorimetry - Coffee Cup Calorimetry Gina...

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Coffee Cup Calorimetry Gina Zanarini; Hannah Mallalieu Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 Submitted on February 12, 2008 In this lab, calorimetry was used to determine the identity of an unknown metal along with heats of solution in water of various compounds. The bond energy of the O-O bond in hydrogen peroxide was also determined using this simple technique. Introduction The heat of solution of a substance is water is the amount of heat absorbed or released when one mol of it is dissolved to make a solution of infinite dilution. The ratio for this experiment is one mol of solute for every 200 mols of solvent. To obtain the proper amount of salt for this ratio the formula used will be w=n x molar mass (Eq. 1). One should also be able to determine whether the overall process was exothermic or endothermic. If endothermic, the temperature drops when the salt is added and the heat of solution is positive. In contrast, if the temperature rises when salt is dissolved in water the heat of solution will be negative making the process exothermic. Using Hess’s law, the heat of solution is found by adding the positive lattice energy with the negative hydration energy. If result is positive, heat of solution is endothermic, and if negative, it is exothermic. Calorimetry is useful for determining temperature changes and therefore energy changes in particular reactions. The calorimeter in this lab will simply consist of 2 Styrofoam coffee cups and a lid. When a salt is added to water in a calorimeter the heat is either absorbed or released by the surroundings. The equation to

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