Question

Discuss the principle and the method of calculation of the following :
Volumetric method for the determination of molecular mass of acids and bases.

Answer 1

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

In volumetric analysis the weight of a reagent necessary to complete a chemical reaction is ascertained by determining the volume of a solution containing a known concentration of the reagent required to react stoichiometrically with the element. From this volume the percentage of the element can be calculated.

Procedure for Volumetric Analysis

1. 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 or pipette containing the titrant.
2. The solution that needs to be analysed needs to have an accurate weighed in the sample of +/- 0.0001g of the material to be analysed.
3. Choosing the right kind of material to be analysed is also very important, as choosing the wrong type of titrant will give us the wrong results. A substance that reacts rapidly and completely to produce a complete solution is chosen.
4. Small quantities of titrant are added to the analyte and indicator till the indicator changes colour in reaction to the titrant saturation threshold reflects the arrival at the endpoint of the titration.
5. The titration has to be continued up until the reaction is complete and the amount of reactant added is exactly the amount that is needed to complete the reaction.
6. Another important step is in measuring the right volume of the standard solution since molarity is a standard metric to calculate the number of moles present in a solution.
7. Based on the desired endpoint, single drops or less than a drop of the titrant makes a difference between a permanent and temporary change in the indicator.
8. If the reagent or reactant that we use is to be made into a standard solution then we can weigh and dissolve the reagent into a solution, so that it is in a definitive volume within a volumetric flask