# Problem: Calculate the pH after 0.020 mole of NaOH is added to 1.00 L of each of the following solutions:a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)b. 0.100 M sodium propanoate (NaC3H5O2)

###### FREE Expert Solution

We are asked to calculate the pH after 0.020 mole of NaOH is added to 1.00 L of each of the following solutions

a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)

Step 1. Calculate the initial amounts of HC3H5O2 in moles before the reaction happens.

molarity (volume) → moles

Recall:

*convert volumes from mL to L → 1 mL = 10-3 L

1.00 L of 0.100 M HC3H5O2

mol HC3H5O2 = 0.100 mol  HC3H5O2

Step 2. Write the chemical equation for the reaction between HC3H5O2 and NaOH.

Reaction:

HC3H5O2(aq)    +   NaOH(aq)               C3H5O2(aq)       +       H2O(aq)
(weak acid)          (base)                    (conjugate base)     (conjugate acid)

Step 3. Construct an ICF Chart.

Step 4. Calculate pH.

Since we have a buffer, we can calculate the pH of the solution using the Henderson-Hasselbalch equation:

pH = 4.28

The resulting solution after the titration has a pH of 4.28.

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###### Problem Details

Calculate the pH after 0.020 mole of NaOH is added to 1.00 L of each of the following solutions:

a. 0.100 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5)
b. 0.100 M sodium propanoate (NaC3H5O2)