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American University of Science & Technology

Department of Laboratory Sciences and Technology

CHE: 205L: CHEMICAL ANALYSIS LABORATORY

Experiment IV
Redox Titration

Name: Helena Al Jawhary / Partner’s Name: Eyad Aridi
Instructor’s Name: Dr Juliana El Khoury
Date of experiment: 10/3/2013
Redox Titration

Objective:

• To learn some technique in volumetric analysis: Redox titration. • To review the stoichiometry of an oxidation-reduction reaction. • To practice the titration technique.
• To determine the concentration of an unknown sodium oxalate (Na2C2O4) solution by titrating it against standardized potassium permanganate solution (KMnO4).

Principle:
Redox reaction is just like an acid-base reaction. An acid can show its acidic properties in the presence of base only. Like acid-base reaction, redox reactions are concerned with the transfer of electrons between species.

One compound has to give electron and oxidizes and another compound has to accept electron and reduces. Hence redox reaction is a combination of oxidation-reduction reaction. Each reaction by itself is known a "half-reaction" and whole reaction is called as redox reaction. For that, the half reactions (oxidation half reaction and reduction half reaction) must be balanced in order to get the fully balanced redox reaction. Titration is a laboratory method of quantitative analysis to determine the concentration of a given sample. Titration is used to determine the concentration of an unknown substance by using standard compound. This method is based on either acid-base reaction or oxidation-reduction (Redox) reaction. Usually potassium permanganate solution is used as a standard solution in such redox reactions. Since potassium permanganate ion is a strong oxidizing agent , hence can be used to analyse the solutions.

The main advantage of permanganate solution in the titration of colorless unknown solutions is that it acts as self-indicating. The color of MnO4- quickly disappears as it is reduced to Mn2+ in the presence of the reducing agent. Finally at the endpoint, all the reducing agent has been used up and next drop of MnO4- solution detected color change where a persistent pink color appears for almost 30 sec. By using the used concentration of the oxidizing agent added, we can figure out the concentration of reducing agent present in the unknown sample using a known concentration of standard compound.

Materials and methods:...
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