An indicator has pKIn = 5.3. In a certain titration, this indicator is found to be 20% ionized in its acid form. Thus, pH of the solution is

HInAcid  form     ⇌      H+    Basic  +    In-   formThus, acid form [HIn] = 0.80 MIn- = 0.20 M    pH = pKIn  +  log  In-HIn = 5.3 + log  0.20.8     = 5.3 + log 14 = 5.3 - 0.60 = 4.7