Acid-base indicators are either weak organic acids or weak organic bases. Indicator change colour in dilute solution when the hydonium ion concentration reaches a particular calur For example. Phenolphthalein is a coloureless stbstance in any aqueous solution with a pH less than 8.3 In between the pH range 8.3 to 10, transition of colour (colourless to pink ) takes place and if pH of solution is greater than 10 solution is dark pink. Considering an acid indicator Hln, the equilibrium involving it and its conjgate base `In^(-)` can be represented as :
`" " underset("acidic from")(HIn)hArrH^(+)underset("basic from")(In^(-))`
pH of solution can be computed as :
`" " pH=pK_(In)+log.([IN^(-)])/([HIn])`
In general, transition of colour takes place in between the pH range `pK_(In+-1.`
An indicator is a weak acid and pH range is 4.0 to 6.0. If indicator in 50% ionized in a given solution then what is the inization constant of the acid ?

Options

A. The pH range of ndicator is 7 to 9
B. Change in pH is 0.96 when 75% yellow colour change to 75% red colour
C. This inkdicator is suitable for the titrationof strong acid vs. strong base
D. pH of indicator is 8.3 when ration of acid from to alkaline from is 2.