I'm not sure if this belongs in the HW section but I'm not doing HW so I'll post it here. My book mentions the auto-ionization constant of water( Kw = [H+][OH-] = 1.0 E-7 ) and shows us how we can use it to find the pH if a strong base is added by solving for [H+]. Later on in the book it introduces you to the acid-disassociation constant( Ka = ([H+][A-])/[HA] ). This makes some of the other information seem inconsistent to me. For example, pOH + pH = 14 is one equation that is given. But this equation was derived using the auto-ionization constant of water. Does this mean pOH = pH = 14 will only work with strong basic and acidic solutions then?