An acid type indicator, Hin differs in colour from its conjugate base (In^(-)) . The human eye is sensitive to colour differences only when the ratio ["In"^(-)]//["HIn"] is greater than 10 or smaller than 0.1. What should be the minimum change in the pH of the solution to observe a complete colour changes. (K_(a) = 1.0xx10^(-5))?

An acid type indicator, Hin differs in colour from its conjugate base

1.	An acid type indicator, Hin differs in colour from its conjugate base (In^(-)) . The human eye is sensitive to colour differences only when the ratio ["In"^(-)]//["HIn"] is greater than 10 or smaller than 0.1. What should be the minimum change in the pH of the solution to observe a complete colour changes. (K_(a) = 1.0xx10^(-5))?
Answer» SOLUTION :`"HIn" HARR H^(+) + In^(-), K_(a) = ([H^(+)][In^(-)])/(["HIn"]) or [H^(+)] = K_(a) (["HIn"])/([In^(-)])` When `([In^(-)])/(["HIn"])=10, [H^(+)]=10^(-5)xx(1)/(10) = 10^(-6), pH = 6` When `([In^(-)])/(["HIn"])=0.1 , [H^(+)]=10^(-5)xx10=10^(-4), pH=4" " :. ` Minimum change in pH = 2