Instructions Experiment 9 Enthalpy of Reactions EXPERIMENT 9- INSTRUCTIONS ENTHA
ID: 1039264 • Letter: I
Question
Instructions Experiment 9 Enthalpy of Reactions EXPERIMENT 9- INSTRUCTIONS ENTHALPY OF REACTIONS PURPOSE: The purpose of this experiment is to become familiar with basic calorimetry experiments. Various reactions will be performed and the enthalpies of those reactions calculated INTRODUCTION: Chemical and physical changes are accompanied by the absorption or release of energy. For example the combustion of methane (natural gas) is a reaction that releases energy as heat (an exothermic reaction). The decomposition of calcium carbonate (limestone) into carbon dioxide and calcium oxide, (lime) is a reaction that absorbs heat as it proceeds (an endothermic reaction). If a reaction occurs in an insulated container, heat can neither enter the container nor escape from it. Thus: If an exothermic reaction is run in an insulated container, the heat produced is trapped inside of the container as thermal energy and raises the temperature of the contents inside the · container If an endothermic reaction is run in an insulated container, the heat needed by the reaction is obtained from the thermal energy on the contents of the container. This lowers the . temperature of the contents. The amount of heat produced or absorbed by many chemical or physical processes can be measured in an insulated container, a so-called calorimeter (this is also described in your textbook). In this experiment we work at constant pressure. The measured change in heat is then related to the enthalpy change of the process (An). The enthalpy change can be calculated from the observed change in heat if the amounts of materials used are known. SUMMARY OF THE CALCULATIONS The important calculation for this experiment is thatExplanation / Answer
1)
2 Na + 2H2O ------------> 2NaOH + H2 ( Exothermic Reaction)
NH4Cl + H2O -----------> NH4+ + Cl- + H2O (Endothermic Reaction)
2)
Heat of reaction (q) doubles its original amount as the no of moles of ammonium nitrate is also doubled.
Enthlapy per mole is a constant and it does not change