Purpose:
Lab Investigation
Topic 8 – Acids and bases
Standardization titration of HCl using KHP
DCP
To standardize a solution of HCl using a NaOH solution that is first
standardized using KHP.
Introduction
As we established in the virtual lab, we can determine the concentration of a strong
acid or base using the standardization titration procedure.
You will use this procedure to standardize a NaOH solution using KHP, then use that
NaOH solution to standardize HCl.
KHP, or potassium hydrogen phthalate, is the acidic salt of phthalic acid, a weak
diprotic organic acid. Its formula is C8H5KO4, and its structural formula is shown
below. KHP is often used in acid-base standardization, because KHP crystals can
easily be weighed accurately.
Figure 1: Structure of KHP. Notice the carbon ring with 2 carboxylic acid groups
attached.
Materials:
 Solutions
o KHP solution (concentration near 0.1 M and known to 4 significant
figures)
o HCl solution (concentration approximately 0.1 M)
o NaOH solution (concentration approximately 0.1 M)
o phenolphthalein
 50 mL burette
 10 mL pipette
 250 mL Erlenmeyer flask
 50 mL beaker
 funnel
 distilled water in wash bottle
Procedure:
0.
1. Rinse all glassware with distilled water.
Rinse beaker with KHP solution.
Rinse burette with NaOH solution.
The Erlenmeyer flask should not be rinsed with either solution.
2. Pipette 10 mL of KHP solution into the Erlenmeyer flask.
Add a few drops of phenolphthalein.
Fill the burette with NaOH solution.
3. Titrate the KHP solution with the NaOH solution.
You should try to get a very pale pink endpoint.
Repeat your titration until you get 3 consistent titration volumes (within 0.1 mL).
4. Repeat Steps 1 to 3 using HCl instead of KHP.
Data Processing and Analysis:
0.
1. Using your data from the KHP/NaOH titrations, determine the concentration of
the NaOH solution and the uncertainty of that concentration.
2. Using this value and your data from the HCl/NaOH titrations, determine the
concentration of the HCl solution and the uncertainty in that concentration.