Problem: What quantity (moles) of NaOH must be added to 1.0 L of 2.0 M HC2H3O2 to produce a solution buffered at each pH?a. pH = pKa

🤓 Based on our data, we think this question is relevant for Professor Longaker's class at UCD.

FREE Expert Solution

When dealing with a buffer, we use the Henderson-Hasselbalch equation:

pH=pKa+logconjugate baseweak acid


The reaction between HC2H3O2 and NaOH is shown below:

HC2H3O2(aq) + NaOH(aq)  C2H32-(aq) + H2O(l)
  (weak acid)                       (conjugate base)

**Na+ is not included in the reaction because it is a neutral ion


Calculate the initial amount of HC2H3O2 in moles:

molarity (M)=molLmoles HC2H3O2 =(2.0mol HC2H3O2L)×1.0 L

moles HC2H3O2 = 2.0 mol HC2H3O2


We need to construct an ICF chart to determine the amounts of the species after the reaction:

Substitute values in the Henderson-Hasselbalch equation:

pH=pKa+logconjugate baseweak acidpH=pKa+log(x2.0-x)pH-pKa=log(x2.0-x)0log=log(x2.0-x)log

**log is a base of 10, when you divide a number by log, you will take 10 raised to the power of the number

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Problem Details

What quantity (moles) of NaOH must be added to 1.0 L of 2.0 M HC2H3O2 to produce a solution buffered at each pH?

a. pH = pKa

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Based on our data, we think this problem is relevant for Professor Longaker's class at UCD.

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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl 2nd Edition practice problems.