Purpose
to show how the transfer of electrons converts a colorless compound solution into a deeply colored solution, thus enriching the understanding of oxidation-reduction reactions.
Data Table
Parts
Part 1 Part 2 |
Observations
A solution of ferrous ammonium sulfate was created by dissolving 0.4g in 4mL of 6M sulfuric acid and diluted to 100mL. This solution was clear and foggy once 50mL of the ferrous ammonium sulfate solution was poured into each beaker. When 10mL of potassium thiocynate solution was added to each beaker, the solution turned a peachy orange color. To the beaker labeled KMnO4, 10mL of potassium permanganate (a purple colored solution) was added; this turned the solution into a deep rich blood red. To the beaker labeled H2O2, 10mL of hydrogen peroxide solution (a clear solution) was added; this turned the solution into a deep rich blood red as well. Slowly, 13mL of stannous chloride solution was added to each beaker. Both solutions became a lighter red than previous and there was an odor present. A clear but hazy solution was formed when 50mL of potassium hydroxide solution was diluted with water to 200mL. After dissolving 5g of dextrose and adding several (3) drops of ethylene blue solution, the solution turned into a royal blue color. The flask was left unattended for five minutes and the solution became clear. When the flask was vigorously shaken, the solution turned regained its blue color but lighter than before. |
Conclusion
Both beakers, KMnO4 and H2O2, went through the same color changes despite the different solutions added. The solutions went from clear to peachy orange to deep blood red to red. It was concluded that this solution reacted because there was an odor present along with the color change. Signs of a chemical change includes odor and color change. A few sources of error could be the systematic errors of the balance beam weighing the grams of ferrous ammonium sulfate. Our group was not sure how much stannous chloride to add, so our interpretation could have been an indeterminate error. For part two, the clear solution turned royal blue. Then, when it was left alone for five minutes, the solution turned clear. When the beaker was shook, the solution turned blue again.
Discussion of Theory
In an oxidation-reduction reaction, a transfer of electrons is involved. Oxidation is the loss of electrons (in which the charge becomes more positive). Reduction is the gain of electrons (in which the charge becomes more negative). The substance oxidized is the reducing agent while the substance reduced is the oxidizing agent. These two, oxidation reaction and reduction reaction, always work as a pair. You can’t have one without the other so it’s called redox reactions for short. A redox reaction consists of two half reactions - an oxidizing half and a reducing half. In a redox equation, each atom is assigned an oxidation number. There are a few rules regarding that such as any single element without a charge always has the oxidation number of zero. In compounds, the oxidation number of the ions must add up to the charge of the compound. The oxidation number equals its charge if it’s a monatomic ion. Oxygen almost always has an oxidation number of -2 except in hydrogen peroxide (where it is -1). Hydrogen always has an oxidation number of +1 in compounds. Fluorine is always assigned an oxidation number of -1. The sum of the oxidation states for an electrically neural compound must be zero. Make sure to adjust the coefficients of reactants to make #e- gained = #e-lost when balancing redox equations.
Heat is produced through redox energy. Electricity can be produced if the reactants are separated. Reactants can only be separated by a salt bridge or by a porous partition. Corrosion is the oxidation of a metal. It’s what happens when something rusts. Many metals develop a thin coating for metal oxide on the outside that prevents further oxidation. Oxidation of most metals by oxygen is spontaneous.
Heat is produced through redox energy. Electricity can be produced if the reactants are separated. Reactants can only be separated by a salt bridge or by a porous partition. Corrosion is the oxidation of a metal. It’s what happens when something rusts. Many metals develop a thin coating for metal oxide on the outside that prevents further oxidation. Oxidation of most metals by oxygen is spontaneous.
Data Analysis Questions
4. When the beaker is shaken, the dextrose re-oxidizes and forms the blue color again. However, since there is less oxygen than before, the color fades more each time. When the beaker is left alone, the oxygen levels decrease and turn back to clear.
5. When the ethylene blue is added, the glucose in the solution becomes oxidized and gives the blue color. The oxygen is released after a while and the equation reverses; therefore, the solution goes back to clear. Shaking the beaker re-oxidizes the dextrose, but eventually all the oxygen gets used up and the solution can no longer re-oxidize with the dextrose.
5. When the ethylene blue is added, the glucose in the solution becomes oxidized and gives the blue color. The oxygen is released after a while and the equation reverses; therefore, the solution goes back to clear. Shaking the beaker re-oxidizes the dextrose, but eventually all the oxygen gets used up and the solution can no longer re-oxidize with the dextrose.