Reaction between and potassium permanganate is a redox reaction in which oxalic acid undergoes oxidation and acts as a reducing agent while potassium permanganate undergoes reduction and acts a a oxidizing agent. The reaction between oxalic acid and potassium permanganate occurs in an acidic medium by adding dilute H2SO4, as permanganate ion is a powerful oxidizing agent in an acidic environment. KMnO4 acts as an indicator where the permanganate ions are deep purple color. MnO4– is reduced to colorless manganous ions (Mn2+) in the acidic medium.
MnO?4+8H++5e??Mn2++4H2O
C2O2?4?2CO2+2e?
2MnO?4+16H++5C2O2?4?2Mn2++8H2O+10CO2
Activation energy of the reactant is the initial energy needed to start a chemical reaction. It also represents the minimum energy needed to form an activated complex during collisions between reactant molecules. In this reaction, it involves bond breakage which requires energy. It is not
sufficient that the molecules just collide, they must collide with sufficient energy so that the reaction may occur. This energy barrier that must overcome is the activation energy. By increasing the temperature not only increases the number of collisions but also increase the energy of the collisions and thus there is greater probability that some of those collisions have sufficient energy to overcome this barrier. When we increase the temperature of the reaction, the time taken for permanaganete to decolorize is shorter as higher temperature implies higher average KE gained by molecules. Collision of molecules per unit time increases, rate of effective collision increases. Rate of reaction increases.
The activation energy is usually represented by the symbol Ea in mathematical equation. In 1889, Svante Arrhenius demonstrated that the rate constant k is related to the temperature of the system by what is known as the Arrhenius equation: k=A e -Ea/RT
where R is the ideal gas constant 8.314 J/(mol K), T is the temperature in Kelvin, Ea is the activation energy in joules per mol, and A is a constant called the frequency factor, which is related to the fraction of collisions between reactants having the proper orientation to form an activated complex. Thus, from the equation, activation energy can be obtained by carrying out experiment. We need to know the value of activation energy so that we know the minimum energy that needed to be provided to the reactants in order to form products.
The precaution steps that have been taken out in this experiment included using constant speed upon stirring the solution until it was decolorized. Therefore, the action of stirring was carried out by the same person from start. This was to avoid the difference in stirring speed of the solution that might cause some changes in the results taken. Another precaution step was by wearing gloves throughout the whole experiment. This was to prevent direct exposure of our bare skin towards corrosive chemicals such as h2so4. Also, the apparatus used such as test tubes were washed before using. This was to eliminate the dust and impurities left in test tubes to increase the accuracy of results.
There are some source of errors that may slightly alter the accuracy of taking the results of this experiment. One of the source of errors that appeared when conducting the experiment was due to human error.This happened when the stopwatch was not started simultaneously as the oxalic acid was poured into the test tube containing KMnO4 and sulphuric acid and when the stopwatch was not stopped immediately when the solution turned colourless. Another human error was the difference in the speed of pouring the oxalic acid into the acidified KMnO4 for each temperature. A source of random error could be the heat loss between the time we took the test tubes out of the water bath to when we mixed them even though we heated them to a constant temperature, in the time that it took to mix the two contents together and stir, some heat was probably lost.
We can improve the accuracy of results taken from this experiment by immediately start the stopwatch once the oxalic acid was poured into the test tube containing mixture of KMnO4 and H2SO4 and also stop the stopwatch when the KMnO4 was being decolorized. Next, we must pour the oxalic acid into the solution using constant speed throughout the experiment. This can be done by the same person. Furthermore, another improvement is by carrying out the experiment in the water bath as we mix the solutions together, this can resuce heat lost to surrounding and the results obtained will be more accurate.
