Solution: A 1.0L buffer solution contains 0.100 mol of HC2H3O2 and 0.100 mol of NaC2H3O. The value of Ka for HC2H3O2  is 1.8×10−5. Calculate the pH of the solution upon the addition of 0.015 mol of NaOH to the original buffer.

Problem

A 1.0L buffer solution contains 0.100 mol of HC2H3O2 and 0.100 mol of NaC2H3O. The value of Ka for HC2H3O2  is 1.8×10−5. Calculate the pH of the solution upon the addition of 0.015 mol of NaOH to the original buffer.

Solution

Determine the pH of the buffer upon addition of strong base using an ICF table and Henderson-Hasselbalch equation.

Step 1. Establish the ICF table

  • HC2H3O2 will appear as the weak acid and C2H3O2-(NaC2H3O2) as its conjugate base
  • Upon addition of the strong base, OH- will consume some of the HC2H3Oto form more C2H3O2-
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