Thermochemistry: an Ice Calorimeter Determination of Reaction Enthalpy

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Thermochemistry: An Ice Calorimeter Determination of Reaction Enthalpy Curtis M. Franklin
Thursday, February 14, 2013
An ice calorimetric measurement was used to determine that a reaction involving solid magnesium metal and 1.00M sulfuric acid produces an experimental a value of ∆H = -226 ± 28 kJ/mol at 0°C. This is about 48.4% lower than the expected value reported at 25°C. 

Many chemical reactions exhibit themselves by exchanging heat energy, either be absorbing heat or releasing it, this heat is energy lost or produced by the system as bonds are formed or broken. These reactions performed under constant-pressure conditions, at 1 atm the energy exchanged is known as the enthalpy change of the reaction. This can be used to measure the potential work energy that a system reaction may possess relative to other reactions and can provide data about the bonding strength of the products and reactants as well as used to predict other reactions that use these products and reactants. A common type of reaction that is chemically assess under laboratory conditions are exothermic reactions, or reactions whose products release heat energy into the environment. They can be ascertained by changes in temperature or by providing energy to molecules. If these molecules are given enough energy they can give visual cues of the reaction strength by changing their phase. Eq. 1 is a predicted as an exothermic reaction, if we can use Eq. 2 as a measurement of its ability to transfer energy we can quantitatively analyze the amount of energy it could possess in its system. Using a technique established in 1783 these properties can be used to measure these heat effects. Eq. 1

Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)
Eq. 2
H2O(s) → H2O(l)
A method known as isothermal calorimetric analysis can be used to perform a quantitative test of the heat released by certain reactions. These experiments are performed by isolating a system typically in ice and...
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