Formal Lab of Enthalpy of Neutralization

Anania Yeghikian 1231077 Partner: Victoria Yue Date of Experiment: Monday, March 11th, 2013 Experiment #5: Enthalpy of Neutralization Objective The neutralization of an acid by a base is most commonly explained as a transfer of protons from the acid to the base. In this experiment, we will study the reaction between a strong acid and a strong base. Because both substances are considered to be strong, they will completely dissociate and will cause the transfer of the proton from the hydronium ion to the hydroxide ion. Therefore, we will determine the enthalpy of neutralization. Procedure With the use of a 100.0 mL graduated cylinder, 50.0 mL of 1.00 M HCl solution were poured into the calorimeter. The lid was then closed. A thermometer labeled ‘‘A’’ was put into the calorimeter with the lid on. After a minute, the initial temperature of the calorimeter was recorded. With use of another 100.0 mL graduated cylinder, 50.0 mL of 1.00 M NaOH were poured into a clean 100 mL beaker. A thermometer labelled ‘‘B’’ was put in the base solution and the reading was recorded. These two temperatures were checked to be within 1 degree Celsius apart. The lid was quickly opened and the base solution was poured into the acidic solution. The lid was put back on and the solution was swirled. The maximum temperature reached by the reaction was recorded and the whole procedure was repeated for a second trial. Discussion The average value for the heat of neutralization per mole for a reaction of a strong acid with a strong base was supposed to be obtained in this experiment. The value we found was -61 KJ/mol. The literary value for this reaction however is -57.9 KJ/mol. This difference is due to some assumptions made when doing calculations. The value for the specific heat capacity of water used was 4.18 J/g x °C rather than that of the actual aqueous solution. We also assumed that the density of the solution was 1.00 g/mL rather than the actual density of the solution which would have been greater. Furthermore, we used a calorimeter constant that was determined experimentally previously to this one, therefore that value could influence results obtained. The variation between the trials was not significantly different. The percent difference calculated was 4.5 %. This is well within the safety line and therefore is not significant. We can safely safe that the reaction was indeed exothermic because of the negative value of the final answer. This makes sense because the temperature reading indicates that there was an increase in temperature. Furthermore, as we were swirling the calorimeter, an increase in temperature was clearly felt.

Ways to improve the results for this experiment are quite simple: better isolation of the calorimeter containing the mixed solution, more precise thermometers, more precise calculations and most importantly very careful experimentation. Conclusion The experiment was quite successful because the objective was met in a satisfying manner. We were able to determine the enthalpy of neutralization of an acidic solution mixed with a basic solution. The percent error was not significantly large and we were able to determine the factors that could help us improve our methods and find a better result next time.