Univerity of the Philippines Diliman
All chemical reactions involve energy. By understanding the behavior and connection of energy flow within a chemical reaction, we can understand and manipulate them to our advantage. The most common form of energy observed during chemical reactions is heat. The reaction may absorb (endothermic) or release (exothermic) heat, depending on the reacting substances. Calorimetry is the process of measuring the heat flow between a system and its environment. The device used to measure this heat transfer is called a Calorimeter. The measurement of this heat is called the enthalpy of the reaction (∆H).
There are two types of calorimeter. The first is a bomb calorimeter where the reaction takes place at constant volume. The other type is the coffee cup calorimeter, wherein the pressure is held constant while the reaction takes place. In the experiment, a modified coffee cup calorimeter is used. It is made up of a Styrofoam ball for insulation, a six-inch test tube, a cork and a thermometer. The setup used is adiabatic, which means, the system is isolated from the surroundings so there is no heat flow.
The first step is to calibrate the calorimeter. Every calorimeter has its own specific heat constant (CCal). NaOH is first poured into the test tube, and then the Ti is measured. Then, HCl is made to react with the base and then the Tf is measured. The net ionic equation of the neutralization reaction is show below.
H+(aq) + OH-(aq) H2O(l) ∆H = -55.85KJ
Using the data obtained (∆T) and the knowledge of the enthalpy of reaction of neutralization of an acid by a base, the CCal can be computed. Equation (1) is an application of the Law of Conservation of Energy, where the heat released by the reaction will be absorbed by the surroundings. Equation (2), which is the formula for computing CCal can be derived from the thermochemical...