Heat of Neutralization, Heat of Solution of Two Salts, and Specifc Heat of a Metal Using a Coffee-Cup Calorimeter

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Calculations and Graphs:

NaOH + HCl → NaCl + H2O

[pic 1]

NH4CL solution

[pic 2]

CaCl2 solution

[pic 3]

H2O and Sn reservoir

[pic 4]

Conclusions, Discussion of Theory, and Error Analysis:

The transfer of heat in the neutralization reaction (NaOH+HCl→H2O+NaCl) showed an increase in temperature. The initial temperature of the NaOH solution was 21.750°C, and the initial temperature of the HCl was 22.830°C. The final temperature of the reservoir after the reaction took place was 27.224°C. The rise in temperature indicates that the reaction took in energy from the surroundings, meaning the reaction was endothermic.

Adding NH4Cl to distilled water and placing it in the calorimeter caused the temperature of the system to drop. The initial temperature before the addition of NH4Cl was 23.035°C, and the final temperature after it was added was 20.692°C. This drop in temperature shows that this process was exothermic, energy was given off to the surroundings. The addition of CaCl2 to distilled water inside the calorimeter, however, caused the temperature of the system to rise from 23.350°C to 25.590°C, indicating that energy was taken in, or that it was an endothermic process.

Through the final process, the specific heat of Sn metal was able to be shown. The value received through this equation was -0.627 J/g*K. The theoretical specific heat of Sn is 0.21J/g*K. This resulted in around 400% error for this part of the lab. A possible cause of this could be not letting the metal fully rise to the temperature of the boiling water. This would have caused final calculations to be off.

Errors that could have occurred in this lab could be not fully dissolving the salts and not closing the lid fast enough after the materials were put into the calorimeter. Not fully dissolving the salts could cause temperature data to be off because if all of the mass of the salt is not fully mixed in, it will not raise or lower the temperature to it’s full potential. Secondly, not closing the lid to the calorimeter fast enough could have caused the temperature of the air to interfere with the temperature data received from the process.

Throughout this lab, the First Law of Thermodynamics was demonstrated. The First Law of Thermodynamics states that energy cannot be created or destroyed, but it can be transferred and changed from one form to another. This lab showed the transfer of energy in the form of heat. Energy was either transferred into the systems from their surroundings (endothermic), or it was transferred from the systems to the surroundings(exothermic). The data recorded in this lab supports this law, within reasonable margins of error.