Purpose.
The purpose of this lab is to show the transfer of electrons during a reaction as well as to show the reduction and oxidation parts of a reaction.
Data Table.
Part
Part I
Part II |
Observations
As the 10mL of potassium thiocyanate solution was added to both of the beakers (KMNO4 and H2O2), the solutions turned a light peachy orange. As 10mL of potassium permanganate solution was added into the KMnO4 beaker, the solution turned a very dark grape colored purple. The solution also emitted an odor which confirmed a reaction had occured. As 10mL of hydrogen peroxide was added to the H2O2 beaker, the solution also turned a dark purple and became thicker. As stannous chloride was added to each beaker, the KMnO4 solution turned back into the light peachy orange color while producing a light yellow (off-white) precipitate. The H2O2 solution also turned back into the light peachy orange color as well and a precipitate was formed in a thickness similar to tomato juice.
When 5g of dextrose and several drops of methylene blue were added into a 200mL solution of potassium hydroxide and de-ionized water the solution turned a very dark royal blue. As the solution was left to rest, it turned colorless. Once the solution was stirred or shaken again, it turned back into the dark royal blue color it had originally been. |
Conclusion.
In conclusion, the reduction-oxidation reaction that took place between Fe+2 and MnO4- was a transfer of 10 electrons. In the redox reaction between Fe+2 and H2O2 there was a transfer of 2 electrons.
Discussion of Theory.
In a reduction-oxidation reaction, or redox reaction, there is a transfer of electrons. The full reaction can be split into separate reduction reactions, where electrons are gained making the charge more negative, or oxidation reactions, where electrons are lost making the charge more positive. The substance reduced is the oxidizing agent, while the substance oxidized is the reducing agent. In a redox reaction, heat is gained and electricity can be produced if the reactants are separated. This can be done by a salt bridge that allows electrons and ions to travel between two separate solutions. In oxidation of a metal, such as iron, the process is called corrosion. Corrosion is usually spontaneous and results in oxidation of only the outside to prevent further corrosion (oxidation) inside of the metal. In a redox equation, each atom is assigned an oxidation number. The oxidation number of any single element without a labeled charge is always zero. In other compounds, the oxidation numbers must add up to the charge on the compound, such as negative one or zero. To create energy, such as the transfer of electrons or ions through the salt bridge, fuel or galvanic cells can also be used to continuously supply the reactants with energy. This type of energy source must be made by a redox equation and can continue until the cells achieve equilibrium. In the Nernst Equation, the potential energy calculated is the maximum potential energy before a current has flowed.
Data Analysis Questions.
4. When the colorless solution of methylene blue is shaken the amount of bubbles and surface area increase. This causes a rise in electron activity levels in the solution where oxidation then takes place and the colorless methylene blue solution turns blue. When the solution is left alone, the electrons are undisturbed which causes the solution to return to clear and colorless.
5. After 10-12 cycles of shaking the colorless solution of methylene blue, it no longer turns blue anymore because the oxygen has reacted. All of the oxygen that was in the solution has been used up and can no longer combine with the glucose in the solution.
5. After 10-12 cycles of shaking the colorless solution of methylene blue, it no longer turns blue anymore because the oxygen has reacted. All of the oxygen that was in the solution has been used up and can no longer combine with the glucose in the solution.