Thermochemistry

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Thermochemistry Lab
Purpose: This lab taught procedures for determining heat of capacity of a calorimeter and measuring enthalpy of change for three reactions. It also enforced methods of analyzing data obtained through experimentation and calculating enthalpy. These procedures are used in the branch of thermodynamics known as thermochemistry which is the study of energy changes that accompany chemical reactions. Concepts from this lab can be used to determine the potential energy of a chemical reaction. Much of the energy people depend on comes from chemical reactions. For example, energy can be obtained by burning fuel, metabolizing of food or discharging a batter. Materials and Methods: All work was done with coffee cup calorimeters, magnetic mixers, standard glassware and hardware. Weights of all materials were obtained using a Metler Toledo electronic scale per the manufacturer’s recommended procedure. Heating of reactants was done with a Thermolyne Type 1900 hot plate set to 500. Temperatures were obtained with a GLX. Experimental Procedure:

Part 1: Determining heat capacity of the calorimeter:
We rinsed all glassware three times with deionized water then we chilled 200mL of deionized water with ice and heated 200mL of deionized water on a hot plate. We measured out 50.0mL of chilled deionized water into a graduated cylinder. We measured and recorded the mass of the empty calorimeter, and then we added the 50.0mL of chilled deionized water and recorded the mass of the calorimeter with the chilled deionized water. We added the magnetic stirrer to the calorimeter and turned on the stirrer to a slow stirring rate. We placed a temperature probe in the calorimeter and placed the lid on the calorimeter. We then measured out 50.0mL of heated deionized water into a graduated cylinder and placed a temperature probe in the graduated cylinder. We recorded the initial temperatures of the chilled and heated deionized water. We added the heated deionized water to the calorimeter and recorded data for 2 minutes. We removed the magnetic stirrer from the calorimeter and recorded the mass of the calorimeter with the chilled and heated deionized water. This experiment was repeated one time.

Part 2: The heat of neutralization of HCl(aq) and NaOH(aq):
We rinsed all glassware, calorimeter and hardware with deionized water three times. We measured 50.0mL of HCl(aq) into a graduated cylinder and 50.0mL of NaOH(aq) into a separate graduated cylinder. We measured and recorded the mass of the empty calorimeter, and then we added the 50.0mL of HCl(aq) to the calorimeter. We recorded the mass of the calorimeter and NaOH(aq). We placed temperatures probes in the NaOH(aq) and the HCl(aq) and adjusted the temperature of the NaOH(aq) until it was within 0.20C of the NaOH(aq). We added the magnetic stirrer to the calorimeter and set it to a slow stirring rate. We added the NaOH(aq) to the HCl and recorded temperatures for 1 minute. We removed the magnetic stirrer from the calorimeter and recorded the mass of the calorimeter with the HCL(aq) and NaOH(aq). This experiment was repeated one time.

Part 3: The heat of solution of NaOH(s):
We rinsed all glassware, calorimeter and hardware with deionized water three times. We weighed and recorded the mass of an Erlenmeyer flask. We added NaOH(s) to the Erlenmeyer flask until we had about 2.00g of NaOH(s). We placed a stopper in the Erlenmeyer flask. We measured 50.0mL of deizonized water into a graduated cylinder, then we weighed and recorded the mass of the calorimeter. We added the deionized water to the calorimeter and recorded the mass of the calorimeter with the water. We added the magnetic stirrer to the calorimeter and set it to a slow stirring rate. We collected temperature data of the deionized water for one minute before beginning experimentation. We added the NaOH(s) to the calorimeter and recorded temperature data for 3 minutes after mixing. This...
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