What equilibrium reaction determines [OH−] and, therefore, the pH of the solution?

3 Answers

• When you have a reaction that occurs between a base. That’s when you can determine the [OH-] ions. These ions will only be present when your dealing with a strong base or weak base. The Arrhenius definition of a base is one that increases the concentration of OH- ions. While an acid increases the concentration of hydronium ions.

  Now when you have a base, you can obtain the pOH of the solution. To find pH you simply subtract the pOH from 14.

  This corresponds to the relationship that

  Pka + Pkb= pkw

  Pkw=14

  Pka is the ionization constant for an acid. Tells us how acidic a solution is

  Pkb is the ionization constant for a base. Tells us how basic a solution is.

  Hope this helped!

• actually you the pH of Co(OH)2 is > 7 because this is base!

• NH3(aq)+H2O(l)<–>NH4^+(aq)+OH^-(aq)