An acid type indicator, Hln differs in colour from its conjugate base (In−). The human eye is sensitive to colour differences only when the ratio [In−][Hln] is greater than 10 or smaller than 0.1. What would be the minimum change in pH of the solution to observe a complete colour change (Ka = 1.0 × 10−5) ?

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

1.	An acid type indicator, Hln differs in colour from its conjugate base (In−). The human eye is sensitive to colour differences only when the ratio [In−][Hln] is greater than 10 or smaller than 0.1. What would be the minimum change in pH of the solution to observe a complete colour change (Ka = 1.0 × 10−5) ?
Answer» An acid type indicator, Hln differs in colour from its conjugate base ( $I n^{-}$ ). The human eye is sensitive to colour differences only when the ratio $\frac{[I n^{-}]}{[H l n]}$ is greater than 10 or smaller than 0.1. What would be the minimum change in pH of the solution to observe a complete colour change ( $K_{a}$ = $1.0 \times 10^{- 5}$ ) ?