[Sheryl Mackie]

    
   

Homework Help Forum: pH of buffer soln

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Posted by Sheryl on Sunday, March 12, 2006 at 5:27pm.

I need to calculate the pH of a buffer solution that is .200 M NH4Cl and .200 M Nh3.

NH4+ + H2O <==> NH3 + H+ is the equation I'm using. Then I made an ICE chart:
NH4+ NH3 H+
.4M .4M 0
-x +x +x
.4-x .4+x x

I was going to use the Henderson-Hasselbalch equation but don't know how to get Ka. Am I proceding in the right direction and where to go from here.

Thank you,
Sheryl

[Borek]

Find Ka in tables (see menu on the left or check pKa and pKb tables) on my site). No need for ICE table - you have both concentrations (of acid and conjugated base) given in the question. Note they are identical.