Ib Chemistry Experiment- Calculating Enthalpy Change

Chemistry Internal judgment Determining the Enthalpy Change of a Displacement Reaction AIM To determine the enthalpy careen for the reaction between copper(II) sulphate and zinc. BACKGROUND THEORY Bond breaking is endothermic while flummox forming is exothermic. The reaction between copper(ll) convert and zinc is exothermic as the energy required to form the bonds of the products is greater than the energy required to break the bonds of the reactants. In an exothermic reaction, heat is given off to the milieu thence, temperature of the surroundings will increase. By measuring the wobble in the temperature and employ the formula Q= mc?T, we hobo await the enthalpy change of the reaction. Equation 1 CuSO4 + Zn ? ZnSO4 Ionic Equation Zn (s) + Cu2+ (aq) ? Cu (s) + Zn2+ (aq) MATERIALS/ tool * 1 insulated Styrofoam cup * Copper(II) sulfate dissolver * Zinc Powder * 1 Thermometer * 1 Stopwatch * unhurriedness Boat * Electronic Balance VARIABLES Independent Dependent Mass of zin c powder and concentration of copper(II) sulfate theme used. Temperature of the solution PROCEDURE 1. Use a pipette to measure 25. 0cm3 of 1. 0 M copper(ll) sulfate to the insulated container. 2. Record the temperature every 30 seconds for 2. 5 minutes 3.Add the excess zing powder (6g) at hardly 3 minutes 4. Stir and record the temperature every 30 seconds for the following 10 minutes. DATA aggregation AND PROCESSING Time (s) Temperature (C) Time Temperature (C) 30 25 390 62 60 25 420 61 90 25 450 60 120 25 480 59 150 25 510 58 180 25 540 56 210 45 570 55 240 52 600 54 270 56 630 52 300 60 660 51 330 61. 5 690 50 360 62 720 49 Therefore, based on the graph shown above (representing the raw data), the change in temperature if the reaction had taken place instantaneously with no heat loss ?T= 70. 5C ? 25C 45. 5C The volume of the copper(II) sulfate solution used was 25cm3, thus the mass of the solution is 25g. Given that the specific heat capacity of the solution is 4. 18 J/K and the temperature change is 45. 5C, as calculated above, thus, the heat, in joules, produced during the reaction can be calculated using the formula Q = mc? T =mass of solution ? specific heat capacity of solution ? temperature change = 25 ? 4. 18 ? 45. 5 = 4754. 75 J In the essay, 25cm3 of 1. 0 mol dm-3 copper(II) sulfate solution was used. Thus, number of moles of the copper(II) sulfate solution used n(CuSO4) = (25? 000) ? 1. 0 = 0. 025 mol Therefore, the enthalpy change, in kJ/mol, for this reaction is ?H = Q ? n(CuSO4) = 4754. 75 ? 0. 025 = -190. 19 kJ/mol Theoretical value/ Accepted Value= ? 217 kJ/mol Thus, percentage mistake = (? 217+190. 19) ? (? 217) ? 100 = 12. 35% CONCLUSION Thus, based on the experiment, the enthalpy change for the reaction is -190. 19 kJ/mol. However, as we can see from the above calculations, the percentage error is 12. 35%. This means that the result is inaccurate from the hypothetical value of -217 kJ/mol by 12. 35%.From the graph, we can also see t hat once zinc is added to the solution (at exactly 3 minutes), the temperature of the solution increases until it reaches the terminal or maximum temperature of 61C. Then, the temperature of the solution gradually decreases until it reaches populate temperature again (temperature of the surroundings). EVALUATION (WHAT CAN BE DONE TO IMPROVE THE EXPERIMENT? ) An assumption do for this experiment is that none of the heat produced by the exothermic reaction is lost to the surroundings and that the thermometer records the temperature change accurately. However, this is very tall(a) to appen in reality, which would explain the percentage error. Thus, to improve the experiment, we can try to minimize the heat loss to the surroundings. This can be done by place a piece of cardboard (or any other insulated material) on top of the cup to cover the top of the cup. A hole can then be made in the cardboard for the thermometer. Another measure that we can take is to ensure that our eye is lev el with the thermometer when interpret the temperature off the thermometer. We can also repeat the experiment a few times and get the sightly of the results recorded. This would allow us to obtain a more accurate value.