Calorimetry: Enthalpy of Neutralization
Calorimetry: Enthalpy of Neutralization
Introduction:
The purpose of this lab experiment was to determine the molar concentration of the unknown HCl by using a coffee cup calorimeter. A coffee cup calorimeter is made of Styrofoam cups with a thermometer that is placed from the top and into the calorimeter to measure the temperature as the reaction happens. The Styrofoam cup used for the calorimeter creates an isolated system as it acts as a heat insulator between the cup and the surrounding. When a reaction happens bonds are created and destroyed causing energy to be released or absorbed. In a constant pressure, like in the coffee cup calorimeter, the change in energy equals to the enthalpy change of the reaction. Because enthalpy change of the reaction equals to the specific heat times the mass times the change in temperature, the amount of heat released or absorbed can be determined by measuring the change in temperature. If the enthalpy change is negative then the reaction is exothermic and if the enthalpy change is positive it is an endothermic reaction (Petrucci, Herring et al. 2011). The heat of the reaction was measured for a the neutralization reaction of four different acids which were 1.994 M HCl, 2.035 M HNO3 , 0.5115 M phenol and HCl with unknown molar concentration.
There are two different situations for the neutralization reaction because the acid used can either be a strong electrolyte or a weak electrolyte. If the acid is a strong electrolyte it will dissociate into ions completely and so if neutralization happens the reaction taking place will be H+ + OH- -> H2O. The heat released for the reaction is the formation of water so the neutralization reaction of the acid will have a heat of the reaction value of -55.90kJ/mol. The neutralizations involving weak electrolytes will partially dissociate into ions. This will mean multiple reactions will govern the overall heat of the neutralization making the heat of the reaction be either smaller or
Introduction:
The purpose of this lab experiment was to determine the molar concentration of the unknown HCl by using a coffee cup calorimeter. A coffee cup calorimeter is made of Styrofoam cups with a thermometer that is placed from the top and into the calorimeter to measure the temperature as the reaction happens. The Styrofoam cup used for the calorimeter creates an isolated system as it acts as a heat insulator between the cup and the surrounding. When a reaction happens bonds are created and destroyed causing energy to be released or absorbed. In a constant pressure, like in the coffee cup calorimeter, the change in energy equals to the enthalpy change of the reaction. Because enthalpy change of the reaction equals to the specific heat times the mass times the change in temperature, the amount of heat released or absorbed can be determined by measuring the change in temperature. If the enthalpy change is negative then the reaction is exothermic and if the enthalpy change is positive it is an endothermic reaction (Petrucci, Herring et al. 2011). The heat of the reaction was measured for a the neutralization reaction of four different acids which were 1.994 M HCl, 2.035 M HNO3 , 0.5115 M phenol and HCl with unknown molar concentration.
There are two different situations for the neutralization reaction because the acid used can either be a strong electrolyte or a weak electrolyte. If the acid is a strong electrolyte it will dissociate into ions completely and so if neutralization happens the reaction taking place will be H+ + OH- -> H2O. The heat released for the reaction is the formation of water so the neutralization reaction of the acid will have a heat of the reaction value of -55.90kJ/mol. The neutralizations involving weak electrolytes will partially dissociate into ions. This will mean multiple reactions will govern the overall heat of the neutralization making the heat of the reaction be either smaller or