0.3g of clotrimazole (C22H17ClN2) was dissolved in 80ml of anhydrous acetic acid. This was titrated with 0.1M perchloric acid using 0.3ml of naphtholbenzein as indicator until the colour changes from brownish-yellow to green.
1ml of 0.1M perchloric acid is equivalent to 34.48mg of clotrimazole (C22H17ClN2).
1st titration= A ml of 0.1M perchloric acid was used.
2nd titration= B ml of 0.1M perchloric acid was used.
Is a blank titration required?
Yes, a blank titration is required in this case. A blank titration is performed to determine any contribution to the titration from impurities or other substances present in the solvent or indicator used, which can affect the accuracy of the titration result.
To perform a blank titration, the same procedure is followed as in the actual titration, but without adding the sample (clotrimazole) to the solution. Instead, only the solvent (anhydrous acetic acid) and the indicator (naphtholbenzein) are used. The volume of perchloric acid used in the blank titration is recorded as "C" ml.
By subtracting the volume of perchloric acid used in the blank titration (C ml) from the volumes used in the actual titrations (A ml and B ml), any contribution from impurities or substances present in the solvent or indicator can be accounted for. This allows for a more accurate determination of the amount of perchloric acid required to titrate the clotrimazole sample.