In order to calculate the enthalpy change of Calcium Carbonate to Calcium Oxide, which is exceedingly hard to control and measure the energy change we must use Hess' law

... Results CaCO Test 1 Test 2 Average Mass of CaCO Used :- 2.48g 2.49g 2.485g Temperature of HCl Initially :- 20°C 20°C 20°C Temperature of HCl after mixing with CaCO: - 22°C 22°C 22°C Total Temperature Change :- 2°C 2°C 2°C CaO Test 1 Test 2 Average Mass of CaO Used :- 1.40g 1.40g 1.40g Temperature of HCl Initially :- 19°C 20°C 19.5°C Temperature of HCl after mixing with CaO: - 38°C 36°C 37°C Total Temperature Change :- 18°C 16°C 17°C In order to calculate the enthalpy change of Calcium Carbonate to Calcium Oxide, which is exceedingly hard to control and measure the energy change we must use Hess' law which states:- "The total enthalpy change for a chemical reaction is independent of the route by which the reaction takes lace, provided initial and final conditions are the same" So therefore on adding Hydrochloric acid, which reacts readily with both, Calcium Carbonate and Calcium Oxide they both form Calcium Chloride crating a enthalpy energy triangle. ?H3 CaCO (s) CaO(s) + CO (g) ?H1 ?H2 CaCl (aq) Therefore:- ?H1 - ?H2 = ?H3 But we cannot enter our results directly into Hess' equation, we must convert them into Enthalpy energies.

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