The correct options are
A pH=pKIn+1
B %[In−]=90.9%
HIn(aq)KIn⇌H+(aq)+In−(aq)
KIn=[H+][In−][HIn]
[H+]=KIn[HIn][In−]
pH=pKIn+log[In−][HIn]
pH=pKIn+log[Ionised form][Unionised form]
When,
[In−][HIn]=10=[Ionised][Unionised]
pH=pKIn+log(10)pH=pKIn+1
Option A is correct.
Also,
[In−]=10[HIn]
%[In−]=[In−][HIn]+[In−]×100
%[In−]=101+10×100=90.9%
%HIn=(100−90.9)%=9.1%
Option B is correct.