Volumetric analysis

Volumetric analysis is a quantitative analytical method which is used widely. As the name suggests, this method involves measurement of the volume of a solution whose concentration is known and applied to determine the concentration of the analyte.

1. Volumetric analysis MD ALTAMASH AHMAD 1850951001 PHARM.D 1 ST YEAR

2. Principle of volumetric analysis Volumetric Analysis is a method of analysis based on titration. In volumetric analysis, a chemical called a titrant is added to a solution of unknown concentration called analyte ( titrand ) together with an indicator that will mark the time at which all of the analyte has been reacted .

3. Procedure of volumetric analysis A typical titration starts with a beaker or flask containing a precise volume of the analyte and small amount of indicator placed underneath a calibrated burette containing the titrant . The titrant used is a primary standard which is most pure and free from water of crystallization is filled in burette The titrand (analyte) is impure and of unknown concentration is kept in conical flask with an indicator to indicate the end point

4. Types of reaction used in volumetric analysis Acid – Base Titrations- Oxidation-Reduction Titrations –

5. 3. Precipitation Titrations – 4. Complex Formation Titrations –

6. DIFFERENT METHODS OF ANALYSIS Direct Titration – In this method, the titrant reacts directly with the analyte usually in the conical flask in the presence of an indicator 2. Back Titration – Back titration is used when the analyte either does not react with the standard solution B or reacts too slowly In this event, a previously known excess of another standard solution E is added to the analyte, and the residue of E after the reaction with the analyte A is complete is titrated with the standard solution B

7. 3. Replacement Titration – Titration by substitution is used when direct titration of the analyte is difficult, as is the case when no suitable titrant or essential indicator is available. In this event, a reaction with an undetermined excess of a suitable reagent E is used to convert the analyte A into another compound D

8. Equivalence point Equivalence point is the theoretical completion of the reaction i.e. the point at which equivalent moles of titrant is added to the analyte solution in the conical flask. end point Endpoint is a physical change in the titration solution as determined by an indicator i.e. colour change, precipitate formation, etc.

9. PRIMARY STANDARD Primary standard is a substance that is 100 % pure or its purity is well known . For example, if the weight required for the preparation of a substance solution is 9.5 g and if the substance powder is 100% pure we weigh 9.5 g and dissolve it in the desired volume to get a standard solution

10. SECONDARY STANDARD A secondary standard solution is a chemical term that refers to a solution that has its concentration measured by titration with a primary standard solution A secondary standard has a less purity than a primary standard. These are less stable and chemically reactive than primary standards. 

11. DIFFERENT METHODS OF EXPRESSING CONCENTRATIONS OF SOLUTIONS Molarity (M ) - Used for quantitative reactions in solution and titrations; mass and molecular mass of solute and volume of solution are known. Molality (m) - Used in determining how colligative properties vary with solute concentration; masses and molecular mass of solute are known. mol/L mol/kg

12. 3. Mole fraction (X) - Used for partial pressures of gases and vapour pressures of some solutions; mass and molecular mass of each component are known . 4. Mass percentage (%) - Useful when masses are known but molecular masses are unknown.

13. 5. Parts per thousand ( ppt ) - Used in the health sciences, ratio solutions are typically expressed as a proportion, such as 1:1000 . 6. Parts per million (ppm) - Used for trace quantities; masses are known but molecular masses may be unknown . 7. Parts per billion (ppb) - Used for trace quantities; masses are known but molecular masses may be unknown.