normality factor and selection of indicator in acid base titration
Sometimes, it becomes difficult to calculate the exact weight of the solute. Under this condition, the concentration of prepared solution becomes different from proposed solution and the term normality factor must be introduced. Mathematically, Normality factor= (Weight taken) / (weight to be taken) Normality factor indicates by how many times the concentration of prepared solution is different from proposed solution. For eg: If we have to prepare 500ml decinormal oxalic acid solution, the weight we have to take is 3.15gm. In lab due to certain difficulties, if weight is taken as 3.10 gm, then normality factor will be equivalent to =3.1/3.15 = 0.98 and concentration is expressed as N/10 (f=0.98) It indicates that the concentration of prepared solution is 0.98 times than that of proposed concentration. Selection of indicator in acid base titration: In acid base titration the completion of reaction is usually indicated by using the third substance (beside titran