Here is a very useful worksheet on calculating the pH and pOH of acids and bases .I have included a log table for you convenience. For example the pH of a solution is given by the formula ph = - Log (6.5 x 10 minus 6). One distributes the log across the parenthesis so we have -(log 6.5 + log 10 minus 6). You look up the log of 6.5 in the table and get .8129. The log of 10 to the minus 6 is simply -6. Finally one distributes the negative sign and you have -.8129 + 6 = 5.19. pOH is simple subtracting that number from 14.