pH = pKa + log (In^-/HIn)
4.55 = 4.95 + log (In^-/HIn)
-0.4 = log (In^-/HIn)
(In^-/HIn) = 0.398 or
(In^-) = 0.398(HIn) so when (HIn) = 1, (In*-) = 0.398
%HIn = [(HIn)/(HIn) + (In^-)]*100 = [1/(1+0.398)]*100 = ?
What color is it at this pH? I don't know because I've never done a titration like that however, it is largely red. So red (a) is mostly right. It will not be b or d. You would expect it to be red to yellow or orange at about 5 or 5.1 So the almost all red will have some yellow or yellow orange mixed in with it. I don't think magenta has orange in it but I don't know. If I had to answer I would choose a as the answer since I don't have a clue what magenta is. :-)