For determining purity of unknown KHP, acid – base titration was used. Molarity of titrant in this case NaOH was standardized as 0.04958(±0.00011) M. Purity of unknown KHP was calculated as 35.88(±0.16) %.
Acid – base titration is typical method of determining unknown figures. Acid – base titration means that by using neutralization between acid and base. Abrupt changing of pH says whether procedure is done or not. pH indicators are tools for determining neutralization is reaching end point. When reaction reaches equivalent point, one of species, titrant or analyte is used up completely and there is no more neutralization. But By pH indicator, there is very few possibility to distinguish equivalent point. When, neutralization reaches at that point, changing pH is too sensitive to distinguish that. Blank titration is one of way to decrease interval between equivalent and end point. Blank titration is executed in solution with no analyte, it involves same volume of diluted water with final volume of mixture of actual titration, pH indicator and titrant. From this titrant, interval is obvious. Before doing titration, standardization of titrant is first step. If concentration of titrant is not exact, final result is not exact. And then, doing titration by standardized titrant is going to be second. • Method
All procedures were taken from Analytical Chemistry Lab – spring2013 First, estimating how much NaOH solution was needed became first step. NaOH solution was prepared in advance. For this step, dried KHP was weighed out 0.2 to 0.3 g and put into 250 mL of Erlenmeyer flask. 25-50 mL of distilled water was added to dissolve KHP. Even though some KHP remained, added NaOH solution would dissolve it. From this estimating titration, mass of KHP neutralizing 40 mL of NaOH solution was computed. Blank titration was performed with 65 mL of distilled water and 2-3 drops of phenolphthalein. Next...