Defining a Standard Solution
A standard solution is a chemical solution in which the concentration of a solute is known with a high degree of precision. This accurately known concentration serves as a reference point for determining the concentration of other unknown solutions.
Section 2: Primary vs. Secondary Standards
There are two main types of standard solutions. A primary standard is prepared by dissolving a very pure, stable, and high molar mass substance (a primary standard substance) in a precise volume of solvent. A secondary standard is a solution whose concentration is determined by titrating it against a primary standard solution.
Section 3: A Practical Example of Preparation
To prepare a primary standard solution of oxalic acid, a chemist would accurately weigh a specific mass of pure oxalic acid crystals. This solid would then be transferred to a volumetric flask, dissolved in distilled water, and the solution would be carefully filled to the flask's calibration mark to create a precise final volume.
Section 4: Importance in Chemical Analysis
Standard solutions are fundamental in analytical chemistry, particularly in a process called titration. By reacting a standard solution with a solution of unknown concentration, scientists can accurately calculate the concentration of the unknown substance. They are essential for quality control, chemical research, and environmental testing.