Calculate the pH at 298K of solutions having the following ion concentrations?

Question

A. [H+]=1.0 x 10^-4M
B. [H+]=5.8 X 10^-11M

for A do you subtract 1.0 X 10^-14 from H+]=1.0 x 10^-4M

Answer 1

For A, no. See an example of both here.
http://www.jiskha.com/display.cgi?id=1268100336