pH of strong base

How to calculate pH of strong bases such as NaOH

If the concentration of the base is above 0.00001 M then the following equation can be used with good accuracy

pH=14 + log (OH-)

Where, (OH-) is the hydroxyl ion concentration which is equal to the strong base concentration.
For example, if we have a 0.001 M sodium hydroxide (NaOH) solution then
pH=14 + log(0.001) plugging that into a calculator gives a pH = 11

If the concentration of the base is less than 0.00001 M another equation has to be used in which the ionization of water becomes a factor.

For example, if the concentration of the base is 0.0000001 M (10 to the minus seven)  applying the above equation gives a value of pH=7! which is not correct to have a neutral pH after adding a base to solution even if the concentration is so small.

Moreover, if the concentration of the base is 0.00000001 M (10 to the minus 8) then applying the above  equation will give a pH=6!! which is not correct at all to have a pH in the acidic region after adding some base.

Comment on this blog for any questions

The following is a link to a site that contains an online pH calculator. You can use it to calculate pH of
solutions with strong acids, weak acids, strong bases, or weak bases.

http://pharmaceutics.me/