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PH of buffer solution

  • Thread starter kasse
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  • #1
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[SOLVED] pH of buffer solution

Homework Statement



Calculate the pH of a solution made by mixing 750 mL 1.00 M NH4+Cl and 250 mL 1.00 M NaOH

The Attempt at a Solution



NH4+ will react with H2O to form NH3 and H2O+. If my calculations are correct, [H+] after the reaction will be 2.07E-5.

Then H+ will react with OH-. But since there's almost no H+ compared to NO-, this reaction is irrelevant. The pOH is therefore

pOH = -log [0.25], and the pH is 13.4

which is wrong. What's my mistake(s)?
 

Answers and Replies

  • #2
Borek
Mentor
28,327
2,713
You should use Henderson-Hasselbalch equation. Your approach neglects shifting of the NH4+ dissociation equilibrium to the right with H+ neutralization.
 
Last edited:

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