Problem: What concentration of NaF is required to make [H3O+] = 2.3 × 10−4 in a 0.300-M solution of HF?

FREE Expert Solution

Henderson-Hasselbalch equation.

pH=pKa+log (conjugate baseweak acid)

 HF is a weak acid
 the anion in NaF is the conjugate base

F- → anion  conjugate base           
       - concentration of F- = concentration of NaF


weak acid + conjugate base buffer


Step 1: Calculate pKa

Ka of HF = 7.24 x 10-4   (can be found in books or online)

pKa=-logKapKa=-log (7×10-4)

pKa = 3.140


Step 2: Calculate pH

pH=-log [H3O+]pH=-log (2.3×10-4)

pH = 3.638


Step 3: Calculate the concentration of NaF.

     Conjugate base = [F-] = [NaF]

     Weak acid = [HF] = 0.300 M

View Complete Written Solution
Problem Details

What concentration of NaF is required to make [H3O+] = 2.3 × 10−4 in a 0.300-M solution of HF?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Buffer concept. You can view video lessons to learn Buffer. Or if you need more Buffer practice, you can also practice Buffer practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Myers' class at NAU.

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry - OpenStax 2015th Edition. You can also practice Chemistry - OpenStax 2015th Edition practice problems.