Lab 5 - Acid-Base Titration
Objective
To determine the concentration of a NaOH solution.
Apparatus:
1. 50 mL burette
2. Burette clamp
3. 25 mL pipette
4. Pipette bulb
5. Small funnel
6. Weighing boat
7. Wash bottle
8. 250 mL volumetric flask
9. 100 mL beaker
10. 125 mL Erlenmeyer flask
11. 250 mL beaker
Chemical:
1. Solid Potassium Hydrogen Phthalate
Solutions:
1. NaOH solution of unknown concentration
2. Phenolphthalein indicator
1
Introduction
In this experiment, a standard solution of potassium hydrogen phthalate,
HKC8H4O4 will be prepared. Given the molar mass for HKC8H4O4 is
204.2 g/mole, the concentration of the standard solution can be determined using
the following equation.

Concentration of HKC H O (M) 
mass of HKC8H 4O4 ( g )
molar mass of HKC8H 4O4 (g/mole)
8
4
4

Volume of solution (L)
The balanced chemical reaction involving potassium hydrogen phthalate and
NaOH is given below.
HKC8H4O4(aq) + NaOH(aq)  NaKC8H4O4(aq) + H2O(l)
Using phenolphthalein as the acid-base indicator, the concentration of the NaOH
solution can be determined.
Concentration of NaOH (M) 
Volume of HKC8 H 4 O 4 used (L)  Concentration of HKC8 H 4 O 4 (M)
Average titration volume (L)
Procedure:
Part A - Preparation of Standard Potassium Hydrogen Phthalate, HKC8H4O4,
Solution
1.
2.
3.
4.
Weigh 3.0 - 3.2 grams of Potassium Hydrogen Phthalate, HKC8H4O4.
Dissolve the acid in about 150 mL of distilled water.
Transfer the acid solution quantitatively into a 250.0 mL volumetric flask.
Fill the flask to the mark with distilled water, and mix thoroughly.
Procedure:
Part B - Acid-Base Titration
1. Obtain about 100 mL of the NaOH solution in a clean and dry beaker.
2. Acclimatize the buret and then fill the buret with the base solution
3. Pipet 25.00 mL of the acid solution into an Erlenmeyer flask. Add about 3
drops of phenolphthalein indicator solution to the acid in the flask.
4. Titrate the potassium hydrogen phthalate, HKC8H4O4, solution with the
NaOH solution from the buret until a pink end point is reached.
2
5. Record the volume of the NaOH solution added to an accuracy of +/- 0.02
mL.
6. Repeat steps 3 to 5 until the titration volumes agree within +/- 0.10 mL.
7. Enter your data clearly on the datasheet and present calculations to show
how you determined the concentration of the NaOH solution in moles/L.
3
Datasheet:
Part A - Preparation of Standard Potassium Hydrogen Phthalate, HKC8H4O4,
Solution
1. Mass of empty weighing boat
2. Mass of empty weighing boat
and Potassium Hydrogen
Phthalate, HKC8H4O4.
3. Mass of Potassium Hydrogen
Phthalate, HKC8H4O4.
4. Volume of solution prepared
4
Datasheet:
Part B - Acid-Base Titration
1. Concentration of standard
HKC8H4O4 solution
2. Volume of HKC8H4O4 solution
used (Part B - step 4)
3. Volume of NaOH solution added to reach the end point.
Trial 1:
Trial 2:
Trial 3:
Trial 4:
1. Final burette
reading (mL)
2. Initial burette
reading (mL)
3. Volume of
titrant used in
titration (mL)
5
Calculations:
Part A - Preparation of Standard Potassium Hydrogen Phthalate, HKC8H4O4,
Solution
Show all work in calculating the concentration of the potassium hydrogen
phthalate, HKC8H4O4, solution in moles/L.
Part B - Acid-Base Titration
Show all work in calculating the concentration of the NaOH solution in moles/L
6