Exothermic reaction Essay

The object of this investigation is to check out the enthalpy commute for the reception CaCO3 (s) i CaO (s) + CO2 (g) by an indirect method acting based on Hess Law. Hesss righteousness states that the enthalpy change for any chemical answer is independent of the route taken provided that the initial and final conditions are identical. So the temperature change during these reactions below tush be rhythmd and the enthalpy changes ? H1 and ? H2 calculated. For Example victimization Hess law with the calculated encourages for ? H1 and ? H2 it is manageable to calculate a value for ? H3. Results Table.Temperature change during reaction The progenys for the temperatures are to the nearest square number as it is unrealistic to measure to a point of a ? C with this type of thermometer and the masses rounded up to 2 decimal places for greater accuracy. Calculations Its possible to use the formula E = mc ? T, where E = cleverness transferred, m = mass of HCl, c= specific commo ve capacity of HCl and ? T = temperature change. This formula can be used for calculating the energy transferred in the following reactions ? ?H1, CaCO3 (s) + HCl and ? H2, CaO (s) + HCl.Seeing as the molar mass of CaCO3 = 100. 00 ?H1 = 420 x (1 x 0. 0250) = 16. 80 kJmol-1 I result non include the last result in my average for ? H1, which is 16. 80 kJmol-1. This is because its flair off the other results and would significantly necessitate my average results, its an anomaly. AVERAGE for the ? H1 for the reaction between CaCO3 + HCl (- 25. 09 kJmol-1) + (- 24. 90 kJmol-1) 2 ?H1 = 25. 00 kJmol-1 This value for ? H1 is negative because heat is befogged to the surroundings. Its an exothermic reaction. Calculations for ? H2 for the reactions between CaO (s) + HCl 1.I will not include the 102. 86 kJmol-1 result in my average for ? H2. This is because its way off the other results and would significantly walk out my average results, its an anomaly. AVERAGE for the ? H2 for the r eaction between CaO + HCl (-128. 05 kJmol-1) + (- 111. 43 kJmol-1) 2 ?H2 = 119. 74 kJmol-1 This value for ? H1 is negative because heat is lost to the surroundings. Its an exothermic reaction. Using Hess round of drinks I will use the value that I extradite calculated for ?H1 and ? H2 to overwork out the value for ? H3. ?H3= ? H1 ? ?H2 = (- 25. 00 kJmol-1) (- 111. 43 kJmol-1)= 86. 43 kJmol-1 This value is positive because heat is clothed from the surroundings. Its an endothermic reaction. I have been told the echt value for ? H3, which is 178. 00. So I will calculate the percentage by which my value is out by the actual value. 178. 00 ? 86. 43 = 91. 57 (91. 57 ? 178. 00) x 100 = 51% Evaluation Errors in procedure When the CaO and CaCO3 were put into the cup on that point was a delay before the eyelid was put on. This could have caused heat to fly the coop out of the cup and the temperature change would not have been as great compared to if there was no delay.