Investigating the reaction between zinc and copper (II) sulphate solution
...r a complete reaction to occur. Experiment Volume of copper (II) sulphate (cm³) Mass of zinc (g) 12345 2020202020 0.20.40.60.81.0 I think the chosen masses will give a good range of temperatures and will work well to give me valid results. Aim The aim of the investigation is to find the amount of energy released during the reaction between zinc and copper sulphate, and whether the amount of energy released increases as the amount of zinc used in the experiment increases. The equation for the reaction is: Zn(s) + CuSO4 (aq) à ZnSO4 (aq) +Cu Hypothesis · I predict that the energy change in the reaction between zinc and copper sulphate would increase as the reaction is exothermic. I now know that the reaction is an exothermic one because of my preliminary experiment. An exothermic reaction is when a chemical reaction releases energy in the form of heat, light or sound. The diagram below is and energy diagram for and exothermic reaction: The reactant energy in this reaction is the energy in the copper sulphate and the zinc. In exothermic reactions the energy of the reactants is greater than the energy of the products. The heat of reaction is the difference between the energy of the products and the energy of the reactants. The product energy is when the reactants change into the products; they have to get rid of their extra energy. They give out energy to the surroundings: this is an exothermic reaction. · I think that if I double the mass of zinc I will double the amount of energy released during the reaction. I think this because if I double the amount of zinc used I will double the number of bonds broken and the number of new bonds to be made and therefore will double the energy change. Apparatus · 1 M Copper (II) Sulphate · Zinc powder · Weighing Scale · Burette · 15 test tubes · Petri dish · Test tube rack · Thermometer · Polystyrene Cups Method The correct amount of copper (II) sulphate, 20cm³, was measured with a burette as this is the most accurate way of measuring liquids (measured to the nearest 0.1cm3). The copper (II) sulphate shall be poured into a test tube and the temperature will be measured with a thermometer. The temperature will then be recorded in order for the temperature change to be measured after the reaction occurs. After this the mass of the zinc shall be measured with an electric balance as it is very accurate (measured to the nearest 0.01g). The powdered zinc shall then be placed into a petri dish, making sure that no powdered zinc shall remain on the weighing scales, as this may affect the results. The powdered zinc shall be placed into a polystyrene cup, which contains copper (II) sulphate and the maximum temperature from the reaction shall be measured with a thermometer and then recorded in order for the energy change to be calculated. A lid shall be placed on top of the cup to make sure little thermal energy is lost. Also the temperature shall be constantly watched in order to make sure that the maximum temperature is not missed. The different amounts of powdered zinc for each test shall be measured (the different masses of zinc which shall be tested are shown in the table above on pg 2). Each of the five different masses of powdered zinc tested shall be repeated three times because it would make the results more accurate and if an anomaly occurs it would be easy to spot, and if there is an anomaly that test shall be done again. An average of the three results shall be produced to give an accurate result. The energy change shall be measured using this equation: Energy change = volume of copper (II) sulphate x 4.18 x mean temperature change Results Volume Copper Sulphate CM3 Mass Zinc g Start Temperature1 degrees Celsius End Temperature 1 Change of Temp 1 Start Temperature2 End Temperature 2 Change of Temp 2 Start Temperature3 End Temperature 3 Change of Temp 3 Average Temp Change Average Energy Change (J) Average Energy Change per mole (J) Percentage Error (%) 20.0 1.0 22.0 31.0 9.0 22.0 31.0 9.0 22.0 31.0 9.0 9.0 752.4 48906.0 77.5 20.0 0.8 22.0 30.0 8.0 22.0 29.0 7.0 22.0 28.0 6.0 7.0 585.2 47547.5 78.1 20.0 0.6 22.0 28.0 6.0 22.0 26.0 4.0 22.0 27.0 5.0 5.0 418.0 45283.3 79.1 20.0 0.4 22.0 25.0 3.0 22.0 24.0 2.0 22.0 26.0 4.0 3.0 250.8 40755.0 81.2 20.0 0.2 22.0 24.0 2.0 22.0 24.0 2.0 22.0 24.0 2.0 2.0 167.2 5340.0 75.0 Analysis From my graph I can see that there is a relationship between the mass of zinc and the average energy change. From my line of best fit I can see that as the mass of zinc increases so does the average energy change. This occurs as if there is a greater amount of zinc powder used; there will be a greater activation energy. Because there is a larger reactant energy more bonds are needed to be broken and made, which means more thermal energy will be given out resulting to a larger average energy change. This proves that my hypothesis is correct, as the reaction is exothermic. My hypothesis was correct as I predicted that the relationship between the mass of zinc and the average energy change would be directly proportional. From my graph I can see that my lien of best fit is directly proportional as it goes through the origin and when the mass of zinc is 0.4g the average energy change is 295J. When the 0.4g is doubled to 0.8g the average energy change is also doubled to 590J. This proves that the mass of zinc is directly proportional to the average energy change. However the actual points plotted on the graph are not directly proportional which shows that my results were slightly inaccurate. The percentage error calculated was very large which shows that my results were not as accurate as they could be. Evaluation From my line of best fit I can see that my results are reliable as there are no anomalies. My line of best fit also goes through the origin and is directly proportional. However from my results table I can also see that my results were inaccurate as the percentage error (the percentage of how far away my results are form what they should be) is very large, around 80%. I tried to make my test fair by using a burette when measuring the volume of copper (II) sulphate which is accurate to the nearest (0.1 cm³). Digital measuring scales were used to ensure that the zinc was measured accurately (to the nearest 0.01g). Whoever was measur...