Titration Methods and Concentration Determination
This page focuses on titration techniques, particularly dosage colorimétrique (colorimetric titration), and the mathematical relationships used to determine concentrations.
Titration is described as a method to determine the quantity or concentration of a dissolved chemical species. The concept of equivalence point is introduced as a crucial aspect of titration.
Definition: The equivalence point in a titration is reached when the reactants are mixed in exact stoichiometric proportions, resulting in complete consumption of both the analyte and titrant.
For colorimetric titrations, the equivalence point is identified by a color change in the reaction mixture.
Example: In a titrage colorimétrique, the end point might be signaled by the solution turning from colorless to pink upon addition of a pH indicator like phenolphthalein.
The document presents the mathematical relationships used at the equivalence point:
- Before titration: n(A) = n(B)
- At equivalence: C_A × V_A = (a/b) × C_B × V_E
Where:
- C_A and C_B are concentrations of reactants A and B
- V_A is the initial volume of A
- V_E is the volume of B added at equivalence
- a and b are stoichiometric coefficients
Highlight: The concentration of the titrated reactant can be calculated using the formula: C_A = (b/a) × (C_B × V_E) / V_A
This relationship allows for the determination of unknown concentrations based on the volumes and concentrations of known reactants.
Vocabulary: Titrage conductimétrique refers to a titration method where the endpoint is determined by measuring changes in the electrical conductivity of the solution.
The page emphasizes the importance of understanding these relationships for accurate quantitative analysis in chemistry.
