Quote Originally Posted by Smudger View Post
I need to prepare 200ml of pH4 solution. I have Sodium Hydroxide,Reagent-Grade pellets,"Not less than 97% Pure,Mol Wt 40.00".
How many grams of this will make up to 200ml of pH4 ?

Like the old saying goes, "You can't get there from here". A pH of 4 is acidic; there is no way a NaOH solution will be acidic.

Calibrations are usually made with buffer solutions. See http://en.wikipedia.org/wiki/Buffer_solution for more info.