Volumetric Analysis

Study design content • sources of acids and bases found in water (may include dissolved carbon dioxide, mining activity and industrial wastes) • volume-volume stoichiometry (solutions only) and application of volumetric analysis including the use of indicators, calculations related to preparation of standard solutions, dilution of solutions and use of acid-base titrations to determine the concentration of an acid or a base in a water sample.

Volumetric Analysis Volumetric analysis involves reacting the sample of unknown concentration with a standard solution – a solution in which the concentration is accurately known. Aim is to find the concentration of a sample experimentally. An acid-base titration is an experimental method that uses specialised equipment to determine the concentration of a solution.

Equipment: Volumetric Flask – used to prepare standard solution (accurately weighed/measured sample of the compound is placed into flask and dissolved in de-ionised water) Pipette – Used to accurately measure an aliquot of the solution of unknown concentration to a conical flask Burette- The standard solution is placed in the burette which delivers accurately known volumes of solution.

Titration Volumes from the burette (titres) are added to the conical flask until the solutions are in stoichiometrically equivalent amounts – the equivalence point. The indicator (usually added to the conical flask) usually changes colour at the end point, about one drop after the equivalence point.

Experimentation Miniscus: White tile: A white tile is usually placed beneath the conical flask to help identify the slightest indicator colour changes.

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