# Problem: Potassium fluoride (100 mL of a 0.4 M solution) was mixed with hydrofluoric acid (100 mL of a 0.4 M solution). What was the resulting pH? If 100 mL of a 0.1 M solution of NaOH was then added, what would the new pH be?A. First pH = 3.15; second pH = 5.21B. First pH = 6.21; second pH = 6.79C. First pH = 6.21; second pH = 8.24D. First pH = 11.2; second pH = 12.3E. First pH = 3.15; second pH = 3.37

###### FREE Expert Solution

We’re being asked to calculate the pH of a solution that is 1.00 M HF and 0.20 M KF.

A solution that contains a weak acid and its conjugate base is a buffer solution. The pH of a buffer solution can be determined using the Henderson-Hasselbalch equation.

We will calculate the pH of the solution using the following steps:

Step 1: Determine the composition of the solution.
Step 2: Calculate the pKa of the weak acid.
Step 3: Calculate the initial pH of the mixture.
Step 4: Determine the initial moles of the weak acid and conjugate base present.
Step 5: Calculate the initial moles of NaOH.
Step 6: Create an ICF chart and determine the final amounts of species present after the reaction.
Step 7: Calculate the pH of the solution.

82% (14 ratings) ###### Problem Details

Potassium fluoride (100 mL of a 0.4 M solution) was mixed with hydrofluoric acid (100 mL of a 0.4 M solution). What was the resulting pH? If 100 mL of a 0.1 M solution of NaOH was then added, what would the new pH be?

A. First pH = 3.15; second pH = 5.21

B. First pH = 6.21; second pH = 6.79

C. First pH = 6.21; second pH = 8.24

D. First pH = 11.2; second pH = 12.3

E. First pH = 3.15; second pH = 3.37