Understanding Chemical Reactions: Titration of Hydrogen Peroxide
School
Brooklyn Technical High School**We aren't endorsed by this school
Course
CHEMISTRY 151
Subject
Chemistry
Date
Dec 12, 2024
Pages
5
Uploaded by PresidentTree4998
Supplies: 0.010 M KMnO solution in a sealed vial; 4 Digital balance; 2 graduatedpipettes; 50 mL glass beaker; 15 mL, 30 mL, and 150 mL beakers; 0.1 M HCl; 2transparent disposable cups; Baking soda; Disposable plate; antiseptic hydrogenperoxide 3% (fresh); recyclable plastic funnel;Principal Concepts 1 and 3: All matter can be understood in terms of arrangements ofatoms, since the chemical elements are the basic components of matter. When thereare chemical reactions, these atoms stay true to themselves.Changes in matter involvethe rearrangement and reorganization of atoms and the transfer of electrons.Investigation:
Procedure Part 11:1. Since you will be working with two reactive solutions, you need to use two separategraduated pipets. Clearly label one pipet for hydrogen peroxide and the other for potassiumpermanganate.2. Label one cup as "distilled water" and fill it with distilled water.3. Position a clean, dry 15-mL plastic beaker on the digital balance and tare (zero) the balance.4. Both potassium permanganate and hydrogen peroxide solutions have a density of 1.00 g/mL,allowing you to easily determine the volume (in mL) of each solution used in the titration.5. Fill one pipet with distilled water and add water drop by drop to the 15-mL plastic beaker untilyou reach a total of 1.00 g of water. Note the number of drops needed. Since water has adensity of 1.00 g/mL, the number of drops to reach 1.00 g will correspond to the drops/mL forthe hydrogen peroxide solution. Set this pipet aside for use with the hydrogen peroxide.6. Dry the cup and repeat the process with the second graduated pipet, which you will reservefor the potassium permanganate solution.Part II:1. Ensure that the washing bottle is filled with distilled water. Label one of the disposable cupsas "waste solution."2. The antiseptic hydrogen peroxide is at a concentration of 3.0% (w/w), meaning there are 3.0grams of hydrogen peroxide in every 100 grams of the solution. This antiseptic peroxide isapproximately 80 times more concentrated than the permanganate solution provided in your kit.For the titration, it is preferable to use solutions with concentrations that are more similar,allowing for comparable volumes during the reaction. Therefore, the 3.0% hydrogen peroxideneeds to be accurately diluted. It is recommended to start with a fresh bottle of hydrogenperoxide labeled as 3%, as older bottles may have lower concentrations due to the slowdecomposition of hydrogen peroxide.
3. Place your clean 150-mL plastic beaker on the balance and tare it to zero. Refill yourgraduated pipet with the hydrogen peroxide solution from the 15-mL plastic beaker. Graduallyadd the 3% hydrogen peroxide solution to the 150-mL plastic beaker until the balance readsapproximately 2 g. It is not necessary to obtain exactly 2.00 g; just record the actual mass inyour notebook.4. Next, add distilled water to reach a total volume of 50 mL, which will also equal 50 grams.Use the washing bottle to carefully add distilled water until the balance displays approximately50.00 grams. Record the actual mass in your notebook. Afterward, swirl the beaker to mix thesolution thoroughly.5. Use the following formula to calculate the molar concentration of your mixture based on Wgrams of 3% hydrogen peroxide diluted to 50.00 L, where W represents the actual mass ingrams of the 3% hydrogen peroxide being diluted. X is the resulting grams of H₂O₂contained inW, 0.0500 L is the diluted volume in liters (adjust this to the actual diluted volume if it differs),34.01 is the molar mass of H₂O₂, and Y is the molar concentration of the diluted H₂O₂expressedin M.Part III:1. Place the 30-mL plastic beaker on a white sheet of paper to serve as a background, making iteasier to observe any color changes during the titration.2. Rinse the graduated pipet for hydrogen peroxide with the diluted peroxide solution from the150-mL plastic beaker and dispose of the rinsing solution in the waste solution cup.3. Refill the graduated pipet with the diluted peroxide solution, then add 30 drops of this solutionto the 30 mL plastic beaker.4. Using the dropping bottle containing the 0.1 M HCl solution, add 35 drops of hydrochloric acidto the glass beaker to acidify the peroxide solution.5. Potassium permanganate is used as a disinfectant; it can oxidize fungi and bacteria and cantemporarily stain skin brown. The solutions can also stain countertops. To protect the countertopfrom spills, place the sealed potassium permanganate vial on a disposable plate. Immediatelyclean up any spills with a paper towel.6. Open the sealed vial of 0.010 M potassium permanganate solution.7. Fill your dry second pipet, labeled for permanganate, with the solution from the vial.8. Add potassium permanganate dropwise to the acidified peroxide solution in the 30 mL plasticbeaker on the white paper, counting each drop. Swirl the beaker after every couple of drops toensure thorough mixing of the solution and facilitate reaction with the potassium permanganate.9. As you approach the endpoint, indicated by the completion of the peroxide reaction, thesolution will maintain a purple or brown color for longer periods. When nearing the endpoint, addonly one drop at a time and swirl after each addition.
10. When the solution stabilizes at a light pink or brown hue, you have reached the endpoint.Make sure to record the number of drops of potassium permanganate solution needed toachieve this.11. Dispose of the titrated solution in the waste solution cup.12. Clean the 30 mL plastic beaker and repeat steps 1 through 11. If your second trial differs bymore than 3 drops from the first trial, conduct a third trial and average the two closest results.13. Pour any remaining peroxide from the beaker into the waste solution cup, then add moreperoxide as needed.14. Neutralize the clear waste solution by adding baking soda until the solution stops fizzing.The waste solution is nontoxic and can be disposed of by rinsing it down the drain.Conclusion:The aim of this lab was to observe and analyze a redox reaction by determining the molarity ofan unknown solution. We conducted a titration of MnO4⁻into a 10 mL solution of Fe²⁺to find themolarity of Fe²⁺. During the redox reaction observed, Fe²⁺was oxidized to Fe³⁺, while MnO4⁻was reduced to Mn²⁺. This indicates that Fe²⁺acted as the reducing agent, and MnO4⁻served asthe oxidizing agent. The balanced equation for the redox reaction in an acidic solution is asfollows:5Fe²⁺+ MnO4⁻+ 8H⁺→ 5Fe³⁺+ Mn²⁺+ 4H₂O.Through various calculations and stoichiometry, we determined the molarity of Fe²⁺to be 0.108M, compared to the actual value of 0.1 M. The comparison shows a percent error of 0%. If anyerrors were present, they likely stemmed from an over-titration of MnO4⁻, leading to anincreased number of moles of Fe²⁺and a corresponding higher molarity reading. Conversely,using less MnO4⁻would have decreased the moles of Fe²⁺, resulting in a lower molarity.Additionally, ineffective stirring of the solution could have delayed the color change, indicatingthe achievement of equilibrium. Despite minor sources of error, the experiment successfullyfulfilled its purpose by allowing us to witness and comprehend the concepts underlying a redoxreaction.The TheoryWhat is Titration?Titration is a widely used laboratory technique for qualitative chemical analysis that helpsdetermine the unknown concentration of a solution (analyte). This method relies on the reactionbetween the analyte and a solution of known concentration (standard solution). The analyte ismeasured in a conical flask using a pipette, while the titrant is contained in a calibrated burette.Some Important Terms in Titration1. Standard SolutionA standard solution is a solution with a known concentration. The substance utilized to createthis solution is referred to as a primary standard. Examples include oxalic acid and sodiumcarbonate.
2. Concentration of a SolutionThe concentration of a solution is defined as the quantity of solute present in a specific volumeof solvent. It can be expressed in various ways.Error AnalysisAlthough we may have rushed through the lab, I believe our results still reflect the actualoutcomes, as we conducted the experiment multiple times.