Standard Solutions – Definition and Preparation of Primary and Secondary Standard Solutions. SI units and their uses.

Preparation of various standard solutions – definition of primary & secondary standards.

Standard solution: A solution with a known concentration of solute is called a standard solution. It is used to compare or determine the concentration of another solution in chemical analysis. Standard solutions play an important role in titration, calibration, and several chemical processes.

Preparation of standard solution

• · Materials and equipment: Analytical balance or digital balance, volumetric flask, beaker, stirring rod or magnetic stirrer, distilled water, and pure solute analytical grade.

• · Procedure:

  • o Solute weighing: Weigh pure solute accurately by using a high-precision analytical balance or digital balance. Record the exact weight of the solute.

  • o Transfer solute into container: Carefully transfer the weighed solute into a clean and dry container.

  • o Solute dissolution: Add a small amount of distilled water or solvent into a container with weighed solute. Stir the mixture using a stirrer or magnetic stirrer. Ensure complete dissolution of solute in a solvent. Add more solvent gradually into a container with constant stirring. Make a homogeneous solution.

  • o Final volume adjustment: Add solution into the volumetric flask. Add solvent carefully into the volumetric flask by using a funnel or dropper to adjust the volume.

Primary Standard

 A primary standard is a stable and highly pure chemical to be used as a reference to prepare a standard solution. It is used for analytical purposes such as titration and other quantitative analysis. Common examples of primary standard substances are potassium permanganate (It is used in redox reactions), sodium hydroxide (It is used in acid-base titration), sodium thiosulfate (It is used in iodometric titration), etc.

Primary standard solution: It is prepared by dissolving accurately weighed primary standard chemicals in a known volume of solvent. It is used in chemistry for accurate and precise titration and other quantitative analyses. The primary standard solution has the following characteristics:

• 1. High purity: Primary standard chemical is used to prepare a primary standard solution. These chemicals are highly pure with purity above 99.9%. This minimizes the error in the quantitative analysis due to impurities.

• 2. Known concentration: The concentration of chemicals in the primary standard solution is accurately determined. It is a reference for use in other chemical analyses.

• 3. Stability: Primary standard solution and primary standard chemicals should not undergo chemical changes over time.

• 4. Ease of handling: Primary standard chemicals should be easy to weigh accurately.

Secondary standard

Secondary standard are the chemicals or solution that is used to calibrate or standardize laboratory instruments and techniques. It is not as pure as a primary standard. Secondary standards are required to ensure the accuracy and reliability of chemical measurements.

Dr Pramila Singh

SI units and their uses.

SI units are also called the International System of Units or Metric system. It has universal acceptability in science, industry, and everyday life. It provides a standardized way to express physical quantities. Some SI units that are in use:

• 1. Meter (m): Meter is a SI unit to measure length and distance.

• 2. Kilogram (kg): A Kilogram is a standard unit to measure weight and mass.

• 3. Litre (L): A Litre is a SI unit to measure volume.

• 4. Mole (mol): The mole is the SI unit for the amount of chemicals. It is used in chemistry to quantify a number of atoms, molecules, or ions in the sample.

• 5. Kelvin (K): Kelvin is the SI unit for temperature. It is used to measure temperature on the absolute temperature scale.

• 6. Ampere (A): Ampere is SI unit to measure electric current.