Thermochemistry and Calorimeter

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Paul O’Malley Lab Partners: Charlie Nguyen and Rupal Chhiba Formal Laboratory Report Laboratory T.A. April Baker IUPUI C125 Section 8005 October 30, 2012 Thermochemistry and Calorimetry Introduction Many things in the real world are a result of thermochemistry. From simple things such as putting ice into your glass of water or burning fuel in your car, thermochemistry pervades our lives. Perhaps after physical exercise, one may use a cold pack for the swelling of a joint or muscle strain. The manufacturing of these little soldiers for athletes relies on the principles of thermochemistry. The mixture of ammonium nitrate and water relies on endothermic properties or in this case when heat is absorbed to create the cold sensation in an ice pack. A device used to measure the quantity of heat transferred to or from an object is called a calorimeter. In most science labs it is more commonly referred to as a Styrofoam cup or a coffee cup calorimeter. In our lab we use a more sophisticated one which included a lid on the cup with an inserted thermometer and a stirrer. Thermochemistry is the study of the heat released or absorbed as a result of chemical reactions. The measurement of the total energy of a thermodynamic reaction is called enthalpy (q). This is the basis for Hess’s law which states that if two reactions are combined to yield a third reaction, the sum of the first two is equal to the third. The energy change is the same whether the process occurs in one step or many. Also the first law of thermodynamics which says that energy can be changed from one form to another, but it cannot be created or destroyed. The change in enthalpy (ΔH) determines if energy is absorbed or released by a chemical reaction. Endothermic reactions have a positive value or enthalpy change and are gaining energy, or the reaction can be exothermic which is a negative value or

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