This laboratory exercise studied the enthalpy change of a chemical reaction between magnesium (Mg) and hydrochloric acid (HCl). The experiment is designed to calculate the energy released from a single replacement reaction (Arami, 1999). The reaction is exothermic, i.e. it gives off heat. An empty calorimeter was weighed and the temperature of the calorimeter recorded. A 0.15g sample of Mg was added to 50 mL HCl in the calorimeter with a thermometer attached. The maximum temperature reached during the reaction was recorded. The final weight of the calorimeter plus its contents was then recorded. The procedure was repeated using 0.25g and 0.35g Mg. Calculations were then made of the change in temperature; mass of the calorimeter plus contents; moles of Mg reacted; heat released in the reaction; the molar heat of the reaction; and the average molar heat of the reaction for the three samples.
Maximum temperature in the calorimeter from the reaction
Mass of calorimeter and its contents after reaction
Mass of contents of calorimeter (mass of calorimeter after reaction - mass of empty calorimeter)
Moles of Mg reacted (g Mg used/grams of Mg/moles {24.3})
Molar heat of reaction (heat of reaction/moles of Mg used)
Average molar heat of reaction for three results
(Arami, 1999; Calorimetry, 2004; Third, 20
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