Final answer:
Water in the flask during titration serves as the solvent for the reactants, allowing dissociation and reaction of the analyte with the titrant, and is necessary to accurately determine the analyte concentration.
Step-by-step explanation:
The presence of water in the flask holding the analyte during a titration is essential as it acts as the solvent for the analyte and the titrant. In an acid-base titration, when titrant of a known concentration is added to the analyte, the resultant pH changes in the solution can be tracked, producing a titration curve. Water provides the medium for the acid or base to dissociate and react with the titrant.
The water's volume should be sufficient enough to allow for the proper dispersion and reaction of the substances but should not dilute the analyte concentration significantly. If the analyte gets excessively diluted, it will require more titrant to reach the equivalence point, which could affect the accuracy of the measured concentration.