Lab Redox Titration

REDOX TITRATION

Luis Gutierrez Chakravarty

Dr.

11/04/13

Chemistry 125

REDOX TITRATION Date of experiment: Friday November 1, 2013 Name: Luis Gutierrez; November 8, 2013 Partner: Sandy Anya

Introduction Redox describes all chemical reactions in which atoms have their oxidation number changed. These reactions often produce a sharp change in the physical properties of the chemicals involved hence are suitable for titration experiments. Titration experiments are used to determine the concentration of an unknown reactant and rely on volumetric measurements. The exact point at which the titration is completed is called the equivalence point and can easily be found in the presence of a sharp color change. Potassium Permanganate KMnO4 is a strong oxidising agent that dissolves in water forming a deep purple solution. The abrupt change in colour when manganese is reduced makes it a useful chemical for titration experiments. In this experiment, the titrant Potassium Permanganate KMnO4 of known concentration is added to an oxalate solution of unknown mixture. The equivalence point of the titration is seen when the deep purple colour of the Permanganate suddenly changes to a light pink. Objective The purpose of the lab was to standardize a solution of potassium permanganate by redox titration with a standard solution of iron(II) ions.

Procedure The experiment consists of a volumetric titration. The titrant is the deep purple Permanganate solution and is reacted with the Potassium Oxalate analyte of unknown mixture.

-

In a 250 ml beaker pour about 150 mL of the permanganate solution

-

Around 0.75 grams of the mixture plus deionized water

-

Pour 75 ml of 0.8 M sulfuric acid into the flask

-

Heat the contents of the flask around 80 degrees Celsius.

-

The titration is carried out and the equivalence point occurs when the deeply coloured solution turns pink for more than 10 seconds.

-

The volume of titrant required for titration is recorded.

-

The experiment is repeated three times

LIGHT PINK

Calculations: moles of solute= (molarity of solution) x (L of solution) mmoles of solute = (molarity of solution) x (mL of solution)

Sources of error: There may be a low percent of error in both trials because of some spill of the substances of the liquid in the process of titration. Reasons why total percentage may have differed from 100% could also be human error in calculations.

Conclusion: The purpose of the lab was to standardize a solution of potassium permanganate by redox titration with a standard solution of iron(II) ions. Throughout this lab we were able to figure out the molarity of MnO4- using different volumes and the molarity of the iron(II) ions and by using different concepts including a titration and half-reactions. Using the half-reactions in the background information, I was able to come up with a balanced redox reaction for the combination of oxalic acid and the potassium permanganate. In this lab, we standardized a solution and then used that solution to determine the number of moles of the oxalic acid. At the equivalence point, we could see that the solution starts to change color so that means that the number of moles of both the oxidizing agent and reducing agent are the same.