Titration
Definition and meaning of Titration in chemistry.
Titration is an analytical technique in which a solution of known concentration (the titrant) is gradually added to a solution of unknown concentration (the analyte) until the reaction between them is stoichiometrically complete. This point is approximated in practice by the endpoint, the moment a chemical indicator changes color, which should closely coincide with the true equivalence point.
In more detail
The analyst carefully adds the titrant from a graduated tube called a buret until an indicator changes color, signaling the endpoint. The equivalence point (the volume at which the titrant added is stoichiometrically equivalent to the analyte present) should closely coincide with the endpoint, though the two are not identical. Titration is widely used in acid-base chemistry (neutralization titrations), redox reactions, and complexometric analysis for metal ion determination. Accurate volume measurements and proper indicator selection are essential for reliable and reproducible results.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Apparatus | Buret (holds titrant), Erlenmeyer flask, indicator |
| Key Principle | At the equivalence point, moles of titrant added are stoichiometrically equivalent to moles of analyte present |
| Common Type | Acid-base titration (neutralization) |
To determine the concentration of an unknown HCl solution, a chemist pipettes 25.0 mL of it into a flask, then slowly adds NaOH solution of known concentration (0.10 M) from a buret until the indicator changes from colorless to pink. If 20.0 mL of NaOH is required, the HCl concentration can be calculated using: (0.10 M)(20.0 mL) = (M_HCl)(25.0 mL), yielding 0.080 M HCl.
Frequently asked questions
What is the difference between the equivalence point and the endpoint?
The equivalence point is the theoretical point at which the titrant added is exactly stoichiometrically equivalent to the analyte present (defined by the reaction's stoichiometry); the endpoint is when the indicator changes color (observed in the lab). They should be very close but are not identical.
Why must the titrant concentration be known precisely?
The unknown analyte concentration is calculated from the known titrant concentration and volumes used, so any error in titrant concentration directly propagates to the calculated result.