Determination of the Enthalpy Change of a Reaction :: GCSE Chemistry Coursework Investigation

Determination of the Enthalpy Change of a replyDetermine the enthalpy transfigure of the caloric decomposition of calcium carbonate by an verifying method based on Hess law.Determination of the Enthalpy Change of a ReactionDetermine the enthalpy change of the thermal decomposition of calciumcarbonate by an indirect method based on Hess law. utilise the proposed method of obtaining results, these values weregatheredReaction 1 CaCO3(s) + 2HCl(aq) CaCl2(aq) + CO2(g) + H2O(l) GRAPH in both cases represents the mean of the data.Using the equation for enthalpy change H = mcTWhere m = Mass of liquid to which commove is transferred to (g)c = Specific heat capacity of aqueous solution (taken as water = 4.18J.g-1.K-1)T = Temperature change (oK)We can thus determine the enthalpy changes of answer 1 and chemical reaction2 using the mean () of the data obtained.Reaction 1 H = 50 x 4.18 x -2.12H = -443.08This value is for 2.51g of calcium carbonate, not 100.1g wh ich is itsmolecular weight.Therefore H = -443.08 x (100.1 / 2.51) = -17670.2 J.mol-1.H = -17.67 kJ.mol-1.Reaction 2 H = 50 x 4.18 x -10.3H = -2152.7This value is for 1.37g of calcium oxide, not 56.1g which is itsrelative molecular mass.Therefore H = -2152.7 x (56.1 / 1.37) = -88150.7 J.mol-1.H = -88.15 kJ.mol-1.Hess law states that 1The total enthalpy change for a chemical substancereaction is independent of the route by which the reaction takesplace, provided initial and utmost conditions are the equal.This means that therefore the enthalpy change of a reaction can bemeasured by the calculation of 2 another(prenominal) reactions which relate directlyto the reactants used in the first reaction and provided the samereaction conditions are used, the results will not be affected.We have the trouble set by the experiment to determine the enthalpychange of the thermal decomposition of calcium carbonate. This isdifficult because we cannot accurately measure how much thermal energyis t aken from the surroundings and provided via thermal energy from a bunsen flame into the reactants, due to its endothermic nature.Therefore using the enthalpy changes obtained in reaction 1 andreaction 2 we can set up a Hess cycleThus using Hess law we can encrypt the enthalpy change of reaction3.Reaction 3 H = Reaction 1 - Reaction 2H = -17.67 - (-88.15) = +70.48 kJ.mol-1.Comparing the value +70.