According to the fact that [H+]*[OH-] is always equal Kw[tex]= 1x10^(-14)[/tex], you can easily find concentration of [H+] by changing from [tex]1*10^(-9) [/tex]to [tex]1*10^(-11)[/tex]
H increases, Kw is constant, therefore [tex]10^-14 / 10^-11 = 10^-3. [/tex]
And you will have [tex]Hence [H+] = 10^-3 [/tex] where pH is 3
