Question

The rapid change of pH near the stoichiometric point of an acid-base titration is the basis of indicator detection. pH of the solution is related to ratio of concentration of conjugate acid. (HNn) and the base `[I n^(-))` forms of the indicator by the expression
A. `log.([In^(-)])/([In^(-)])= pK_(In) -pH`
B. `log.([HIn^(-)])/([In^(-)])= pK_(In) -pH`
C. `log.([HIn^(-)])/([In^(-)])= pH_(In) -pK_(In)`
D. `log.([In^(-)])/([ H In^(-)])= pH_(In) -pK_(In)`

Answer 1

Correct Answer - D
`pH = pK_(a)+log. (["Conjugate base"])/(["Acid"])`
`:. pH - pK_(In)=log. ([In^(-)])/([H In])`