Catherine Callahan Chem 112 Experiment 4 Report Objective The purpose of this experiment was to test observe and analyze the effect of temperature on the rate of reactions This was tested specifically by the reaction of potassium permanganate with oxalic acid With prior knowledge we know that increasing temperature speeds up the rate of chemical reactions through faster moving particles resulting in a higher frequency of collisions but we never pinpointed as to why this happens It turns out that molecules not only have to collide they must collide with sufficient energy to overcome a specific barrier This energy barrier that must be overcome is called the activation energy Increasing collisions increases the probability that more collisions will overcome this barrier In this specific reaction the barrier that must be overcome is the permanganate molecule that goes from MnO4 to Mn2 in its reaction with oxalic acid This bond breakage requires sufficient energy and we experimented to find the quantity of energy required to break this bond Our data is shown in the table below KMnO4 mL H2C2O4 mL Temperature C 10 10 10 10 20 20 20 20 0 10 20 30 Reaction Time Trial 1 s Reaction Time Trial 2 s Average Time s 28 15 min 1689 s 10 15 min 609 s 27 58 min 1654 8 s 7 35 min 441 s 27 865 min 1671 9 s 8 75 min 525 s 5 11 min 306 6 sec 4 41 min 264 6 s 4 76 min 285 6 s 2 42 min 145 2 sec 2 58 min 154 8 sec 2 5 min 150 s Calculations KMnO4 Molarity of KMnO4 x volume of KMnO4 used total volume 0 021 M x 10mL 30mL 0 007 M H2C2O4 Molarity of H2C2O4 x volume of H2C2O4 used total volume 0 50M x 20mL 30 mL 0 333 M Rate if reaction KMnO4 time 0 007M 1671 9 s 0 00000419 or 4 19E 6 M s K rate KMnO4 x H2C2O4 4 19E 6 M s 0 007 M x 0 333 M 0 0017975 or 1 8E 3 M s T K 273 15 283 15 293 15 303 15 1 T 1 K 3 66 E 3 3 53 E 3 3 41 E 3 3 30 E 3 k 1 8 E 3 5 72 E 3 1 05 E 2 2 0E 2 ln k 6 32 5 17 4 55 3 91 Activation Energy Slope 7088 Ea R 7088 8 314jmolK 58929 632 1000 58 9kJmol 1 T C 0 10 20 30 Graph Discussion The value of the calculated activation energy was measured by taking the slope change in ln k over the change in 1 T and multiplying it by the ideal gas constant 8 314 J mol k This value is negative meaning that the reaction will proceed without any additional energy from another source The activation energy ultimately tells us the minimum amount of energy required for a reaction to occur Hence the lower the activation energy the faster the reaction In this experiment the reaction s activation energy should be lower than the typical bond energy because we are increasing the temperature therefore speeding up the reaction and lowering the activation energy because less energy is needed to complete the reaction Overall our experiment was successful because the graph was linear and yielded a negative slope as predicted
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