I have .20M of a solution NaCN. Ka for HCN = 4.0 x10 10. How do I solve for pH?© BrainMass Inc. brainmass.com March 4, 2021, 5:53 pm ad1c9bdddf
For these questions you must learn the general formula for a weak acid (and weak bases, just a little adjustment).
Ka = [H+][A-]/ [HA] which is true for any and all weak acids because...
HA --> H+ + A- and any K ...
This solution is provided in 258 words and uses the formula for a weak acid/base to find pH.