Which device is used for precise dilutions and preparation of standard solutions?

• A. Desiccator
• B. Beaker
• C. Volumetric flask
• D. Graduated cylinder

Answer: (C)

Precise dilutions and standard solutions rely on using a container that fixes a known final volume with very tight accuracy. A volumetric flask is made with an accurately calibrated capacity and a narrow neck that is marked to indicate the exact volume when filled to that line. When you fill to the mark, the internal volume is known to a small tolerance, so the concentration of any dissolved substance in the flask is reproducible. This is crucial for standard solutions used to calibrate instruments or determine unknown concentrations.

In practice, you weigh or dissolve the solute, transfer to the volumetric flask, rinse the transfer vessel with solvent to bring all material into the flask, and then add solvent until the bottom of the meniscus sits exactly at the calibration mark. That precise volume defines the final solution’s concentration.

A desiccator is for drying or storing moisture-sensitive samples, not for accurate volume measurements. A beaker is convenient for rough mixing and estimating volumes but has large tolerances. A graduated cylinder offers more precision than a beaker but is still not designed for producing solutions with a precisely known final concentration.