The ionisation constant of an acid base indicator is 3' 10^(-5). The acid from of the indictor is red and the basic form is blue. By how much must the p^(H) change in order to change the indicator from 75% red to 75% blue?

The ionisation constant of an acid base indicator is 3' 10^(-5). The a

1.	The ionisation constant of an acid base indicator is 3' 10^(-5). The acid from of the indictor is red and the basic form is blue. By how much must the p^(H) change in order to change the indicator from 75% red to 75% blue?
Answer» `1.95` `2.95` `0.95` `3.95` SOLUTION :`HIn hArr H^(o+) + In^(o+)` `K_(In)=K_(n)=([H^(+)][In^(-)])/(HIn),[H^(+)] = Ka(["acid"])/(["BASIC"])` for `75%` red, `[H^(+)] = ((3xx10^(-5))(75))/(25) = 9 xx 10^(-5), p^(H) = 4.05` The change in `p^(H) = 5 - 4.05 = 0.95`