Chemical Thermodynamics Report.docx - Chemistry Lab 114 R5...

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Chemistry Lab 114 – R5Chemical Thermodynamics: Heat of Formation of Magnesium OxidePurposeThe purpose of this experiment is to determine the enthalpy of formation of solid magnesiumoxide (MgO) and to determine the specific heat of an unknown metal. Because it is not feasibleto directly measure the amount of heat given off in the formation of magnesium oxide, theenthalpy of formation will be determined from two individual steps in this reaction. Both of theseexperiments utilize the principles of calorimetry, which state that the amount of heat absorbed bya solution in a calorimeter is equal to the amount of heat released by the reaction.Theory The theory behind the first part of the experiment is to utilize Hess’s Law to calculate theenthalpy of formation (ΔH) for a reaction that is not physically feasible from the enthalpies offormation for two individual reactions that are physically feasible and ultimately lead to thereaction of interest. Hess’s Law states that if a reaction is carried out in a series of steps, theenthalpy of formation for the reaction will equal the sum of the enthalpy changes for theindividual steps. Therefore, the enthalpy of formation for a reaction that is difficult to directlymeasure can be determined via the enthalpies of formation for intermediate reactions that can bedirectly measured. The enthalpies of formation for the intermediate reactions will be measuredusing a standard Styrofoam-cup calorimeter, which is a device that prevents heat from escapingduring a chemical reaction and, therefore, enables an accurate determination of the enthalpy offormation for a reaction. However, it is important to use dry and clean cups for the calorimeter,measure solution volumes precisely, and determine temperature changes precisely in order toobtain accurate results while using the calorimeter. Similarly, the theory behind the second partof the experiment is to utilize a calorimeter to determine the amount of heat given off by anunknown metal to calculate the specific heat of the metal. The specific heat of a metal is anintensive property that is characteristic of that metal and can, therefore, be used to identify themetal. Due to its high specific heat, water will be used in the calorimeter as the solution to absorbthe heat given off by the metal, which can then be determined from the temperature increaseobserved in the water. Procedure for Enthalpy of Formation for MgO1.Set up the Styrofoam-cup calorimeter by inserting the small cup into the larger cup. Makesure both cups are clean and dry before use.2.Prepare 250 mL of 1M HCl solution from the 3M stock solution.3.Transfer exactly 100 mL of this diluted solution into the calorimeter. 4.Clean a piece of magnesium ribbon with steel wool and weigh a piece of about 0.25 gramsand record the weight.

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Term
Fall
Professor
N/A
Tags
Thermodynamics, Enthalpy, Heat, Formation of Magnesium Oxide

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