CHM3120C Analytical Chemistry Lab
Lab 3. Practice Titration, Analysis of weak acid Potassium Hydrogen Phthalate (KHP)
Required Reagents and Supplies:
minimum 300 mL of 1 N NaOH solution (volumetric
standard), deionized water, parafilm, minimum 36 g of dried KHP, phenolphthalein indicator,
200 mL of 6 M HCl solution, Na
, and the pH paper.
The purpose of this laboratory exercise is to assist you in mastering some
fundamental techniques that you will use throughout this course: specially weighing and
titrating. You will standardize the solution with primary standard: 0.1 M NaOH solution with
KHP. That is, you will use known amounts of the primary standards to determine the exact
concentration of your base (i.e. 0.1023 M).
A Primary standard is generally a solid that can be obtained in extremely high purity (greater
than 99.99%). Typically, a known amount of this solid is weighed into Erlenmeyer flask and
dissolved in about 50 mL of water. After adding the appropriate indicator, this solution is then
titrated with the solution to be standardized. By knowing the exact weight of the primary
standard used (to at least four digits), one can determine exactly how many moles of base were
required for neutralization. Reading the burette to
0.01 mL allows the analyst to calculate a
molarity of base that is accurate to four significant digits.
Although determining the molarity of NaOH is an important goal, primary importance is the
development of good technique.
Part 1 (start from step d)
Preparation of 0.1 M Carbonate-free Sodium Hydroxide
Each student will use about 25 mL of 1M standardized NaOH solution for part 2.
Boil ~ 250 mL of deionized water (may require more than one beaker) for approximately
5 minutes in beakers. This is to remove any remaining carbon dioxide in the water. Do not
worry even if you have less than 250 mL of water after boiling, because you are not