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To Determine the Enthalpy Change of a Reaction.
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| Submitted: Wed Sep 17 2003
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TO DETERMINE THE ENTHALPY CHANGE OF A REACTION PLANNING. CaCO3 --> CaO + CO2 This is the equation for the reaction I intend to find the enthalpy change for. As this particular reaction is very difficult to measure the enthalpy change by carrying it out (the decomposition of CaCO3 needs a temperature of over 800°C), I must use another method and it uses Hess' Law. Hess' Law States: "The enthalpy change for any chemical reaction is independent of the intermediate stages, provided the initial and final conditions are the same for each route." CaCO3 CaO + CO2 CaCl2 + CO2 + H2O In simpler terms, the main point of Hess' Law is that the total enthalpy change for the indirect route of a reaction is the same as the direct route, i.e. ?H1 = ?H2- ?H3. The diagram above represents a Hess Cycle or a Thermochemical Cycle. By knowing the enthalpy changes in two parts of the cycle, it is possible to calculate the third part...
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