Heat of formation of magnesium oxide

Topics: Thermodynamics, Chemical reaction, Energy, Temperature, Enthalpy, Heat / Pages: 4 (983 words) / Published: Jan 15th, 2014
Heat of Formation of Magnesium Oxide

Objetive:

To determine the heat formation of MgO (Magnesium Oxide) using Hess’s Law, which states the heat within a chemical reaction is independent of the pathway between the initial and final states.

Introduction: Chemical reactions require heat energy to complete, called an endothermic reaction, or produce heat energy, and thus called an exothermic reaction. The heat energy produced by such reactions can be measured using a calorimeter, a piece of equipment that can isolate the reaction in an insulated container. Using the calorimeter one can then determine the rise and fall in temperature of the reaction. When this temperature change is multiplied by the heat capacity, the amount of heat needed to raise the temperature of a body by one degree, we can measure the change in converting our initial components (reactants) to their respective products. In this experiment we will measure the amount of heat released from 3 reactions (ΔHA ΔHB ΔHC) and calculate the sum of all 3 reactions to determine ΔHT, which will give us the heat formation of MgO. If Hess’s law holds true and barring minimal experimental error, the pathway we use to determine ΔHT should have no bearing on our calculation matching the accepted calculation of MgO.

Methods:

As per lab manual we used a calibrated calorimeter (using a rounded end thermometer so as to not puncture a hole in the calorimeter) to determine the heats of reaction for Magnesium (Mg) with Hydrochloric Acid (HCl) and Hydrochloric Acid with Magnesium Oxide (MgO). Then using mathematical formulas we were able to calculate the heat formation of MgO, which is measured in kJ/Mol.
Since both reactions are in dilute water solutions of HCl it was necessary to know the heat capacity of water, but because some heat would be transferred to the calorimeter whose heat capacity was unknown, we had to record a correction factor (x) based upon the specific heat of water using the

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