Calorimeter Experiment

INTRODUCTION

Given appropriate chemicals and equipment, the specific heat capacity and molar mass of a metal, enthalpy of neutralization of an acid and base, and the enthalpy of solution of an unknown salt can be determined by following specific procedures. All of these procedures require the use of a calorimeter, which are of two types: a bomb calorimeter and a coffee cup calorimeter. Calorimeters are simply devices used to measure the amount of heat gained or lost in a system. Although this is not completely true, they are treated as isolated systems. A simple coffee-cup calorimeter can be constructed using two Styrofoam cups nested inside each other. The Styrofoam prevents heat loss to the surroundings, which makes it an ideal calorimeter.
This part of the experiment yielded an exothermic reaction. The purpose was to calculate the specific heat capacity and molar mass of the zinc metal. The specific heat capacity was found to be 0.197 J/g °C with a percent error of -49.5%. The molar mass was found to be 127 g/mol with a percent error of 94.2%. Possible sources of error inherent to this segment of the experiment were the fact that when the temperature of the solution was being measured, the calorimeter was placed near the hotplate by mistake. The heat from the hotplate could have transferred to the calorimeter, which would result in an increased temperature. This explains why the percent error for the specific heat capacity was negative. Another source of error is that the hole in the lid of the calorimeter gradually expanded, which resulted in a heat loss from the calorimeter. A second source of error is that the graduated cylinder used at the beginning of the experiment was not clean. The dust particles in the graduated cylinder could have reacted with the water or with the metal, resulting in a change of mass of the overall solution. This would result in the specific heat capacity of zinc being altered, due to the fact that the dust particles most likely have a specific heat capacity different than that of
These reactions were exothermic. The purpose of this part of the experiment was to calculate the heat of neutralization per mole of water. Two trials were conducted using HCl to form NaCl salt. The heat of neutralization per mole of water was found to be -55 kJ/mol with a percent error of -4.51%. Two trials were conducted using HNO3 to form NaNO3 salt by the two students mentioned in the references section. The heats of neutralization per mole of water were found to be -57.6 kJ/mol, with a percent error of -4.51%. Although the percent errors weren’t very large, they were still off. These could have occurred due to the fact that not all of the acid solution was poured into the calorimeter. Some of the acid could have reacted with the air, and this would decrease the volume of acid which actually mixed with the base, resulting in an increased heat of neutralization. A second source of error was that in the experiment where HCl and NaOH were being mixed, one drop of NaOH was lost by accident which the NaOH solution was being poured into the calorimeter. This would result in too much acid solution, which means that not all of the acid completely reacted with the base. This, also, would increase the heat of