Thermochemical reactions laboratory report: INTRODUCTION
Chemical reactions are generally accompanied by some heat change. The chemical reactions which involve energy changes are referred to as thermochemical reactions. During many chemical reactions, energy is converted to heat energy and result in increase in the temperature of the surrounding. These reactions are called exothermic reactions. Some chemical changes absorb energy from the surrounding and are known as endothermic reactions.
Enthalpy change always result from changes in a chemical system, hence, the heat changes are classified according to the type of chemical reactions. For instance, enthalpy change from the dissolution of a substance is called the heat of solution. The enthalpy change involved in a chemical change stays constant regardless of the route taken during the chemical change provided the initial and final conditions remain the same. This is the Hess’ law of constant heat summation.
Thermochemical reactions laboratory report: PROCEDURE
1. The heat of neutralization of HCl (aq) with NaOH (aq).
Using a graduated cylinder, about 50.0mL of 1.0M HCl was carefully measured and transferred into the calorimeter that was setup as instructed. Then 50.0mL ofNaOH into a small beaker. The stirring plate was then switched on and the stirring bar was adjusted until it spun rapidly and smoothly. The time duration was changed to 180 seconds in the LabQuest. The probe was checked to ensure it was placed properly in the calorimeter and the green arrow in the LabQuest was pressed to continue with the experiment. NaOH solution was added into the calorimeter after 40s. After data was taken, a graph was projected onto the display and the data was then analysed as instructed.
2. The heat of solution of NaOH (s)
About 4.00g of solid NaOH was carefully weighedusing a weighing bottle. Then 100mL of distilled water was carefully added into the calorimeter. The stirring plate was switched on and the stirring bar adjusted until it spun quickly and smoothly. The duration on the LabQuest was reset to 480s r. The probe was checked to ensure that it was beneath the liquid level. Solid NaOH was poured into the calorimeter after 40s. After data was obtained, it was then analysed using the procedure given.