At Alsadek Scientific Association
Prepared by: Zainab Alfakih & Jinan Krayem
Teacher: Dr. Hiba Nassar
Oxidation Reduction reactions are chemical reactions in which substances undergo changes in oxidation state. Oxidation is defined as the loss of electrons (or an increase in oxidation state) and reduction as the gain of electrons (or a decrease in oxidation state). In acid base titrations, equivalent amounts of acid and base must be used for exact neutralization at the titration endpoint. In oxidation-reduction reactions, there is a similar equivalence between oxidizing and reducing agents. In order for a redox reaction to be valid, it should be unique, complete spontaneous and rapid. In titration:
* Reaction is unique. The condition is indispensable to establish a relation between the amounts of matter of the reactants involved. * Reaction is complete. The reagents, which are introduced in stoichiometric proportions, should be completely consumed at equivalence. This is expressed by a difference in potentials of the two couples involved, ∆E0, greater than 0.3V. * Reaction is spontaneous and rapid. Reactants should react spontaneously and instantaneously as soon as the mixed.
* To use a standardized acid solution to determine the concentration of a base solution. * To learn the technique of titration
III. Theoretical Study:
a. Definition of titration:
Volumetric titration consists of the addition of a determined volume of titrating solution with known concentration C1 to an exact volume of solution with unknown concentration C2 to be determined. Volumetric titration is based on a reaction, which occurs between the titrating solution (titrant) and the solution to be titrated (analyte). Redox reactions are used to realize such titrations. b. Definition of equivalence point:
The equivalence point corresponds to the end point of titration reaction. It is determined by a change of color in the reaction, the reactants have reacted in stoichiometric proportions. If either the titrant or analyte is colored, the equivalence point is evident from the disappearance of color as the reactants are consumed.
a. Balanced redox equation:
b. Concentration of H2SO4:
Given: H2SO4M=98.08 mol.l-% by mass=98%d=1.84 Kg.l-=1840g.l-
→CH2SO4=%by mass×dsolution100×MH2SO4=98×1840100×98.08=18.38 mol.l-
c. Dilution of H2SO4:
Given: H2SO4C1=18.38 mol.l-V1=??
d. Mass of KMnO4 (titrant):
C KMnO4=n KMnO4V KMnO4=m KMnO4M KMnO4V KMnO4
e. Mass of FeSO4 (analyte):
It is only used for the comparison at the end of the reaction.
* Erlenmeyer flask
* Pipet bulb
* Filter funnel
* Distilled water
* FeSO4 solution
* KMnO4 solution
Note: In order to get an exact and precise result of the titration, all glassware used in the titration should be cleaned with distilled water. All the equipment used should be kept in good state of cleanness.
Figure 1: Experiment Setup.
A. Preparation of 0.3g potassium permanganate:
1. Dissolve about 0.3 g of KMnO4 in 250 mL of distilled water. 2. Keep the solution at a gentle boil for about half...