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

Determination of the total heat Change of a receptionDetermine the heat content motley of the caloric decomposition of calcium carbonate by an indirect method base on Hess truth.Determination of the Enthalpy Change of a replyDetermine the total heat change of the thermal decomposition of calciumcarbonate by an indirect method based on Hess law.Using the proposed method of obtaining results, these entertains 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 heat is transferred to (g)c = Specific heat capacity of aqueous solution (taken as water supply = 4.18J.g-1.K-1)T = Temperature change (oK)We drop thus determine the enthalpy changes of reception 1 and reception2 development 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 carbo nate, not 100.1g which 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 chemicalreaction is independent of the route by which the reaction takesplace, provided initial and final conditions are the same.This means that therefore the enthalpy change of a reaction can be measuringd by the deliberation of 2 other reactions which relate directlyto the reactants used in the outgrowth reaction and provided the samereaction conditions are used, the results will not be affected.We have the problem 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 poweris ta ken from the surroundings and provided via thermal energy from aBunsen 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 calculate the enthalpy change of reaction3.Reaction 3 H = Reaction 1 - Reaction 2H = -17.67 - (-88.15) = +70.48 kJ.mol-1. examine the value +70.