pH Titration Curve

Plotting a complete acid-base titration curve with pH meter

Titrations Intermediate (High School) 50 min ~$15.00

Objective

Record pH measurements during an acid-base titration and construct a complete S-shaped titration curve showing the equivalence point and buffer regions.

Background

A pH titration curve provides far more information than an indicator-based titration. The S-shaped curve reveals the buffer region, half-equivalence point (where pH equals pKa for weak acids), and the sharpness of the equivalence point. This experiment compares the curves of strong and weak acids.

Safety Warnings

  • HCl and NaOH are corrosive
  • Wear safety goggles and gloves
  • Handle the pH electrode carefully — it is fragile

Required PPE

goggles gloves lab_coat

Materials

  • Hydrochloric acid (HCl) (50 mL)
    0.1M
  • Sodium hydroxide (NaOH) (100 mL)
    0.1M
  • pH buffer solutions (3 bottles)
    pH 4, 7, 10 for calibration
  • Distilled water (200 mL)

Equipment

50 mL burette Burette stand and clamp 250 mL beaker pH meter with electrode Magnetic stirrer 25 mL pipette Graph paper

Procedure

1

Calibrate the pH meter using the three buffer solutions (pH 4, 7, 10).

5 min Handle pH electrode gently
2

Pipette 25.0 mL of 0.1M HCl into the beaker. Record the initial pH.

3 min
3

Fill the burette with 0.1M NaOH. Record the initial volume.

3 min
4

Add NaOH in 1.0 mL increments, recording the pH after each addition. When pH changes rapidly, switch to 0.2 mL increments.

25 min
5

Continue adding NaOH until the pH is above 12. Add a few more points past the equivalence point.

5 min
6

Plot pH (y-axis) versus volume of NaOH (x-axis) to construct the titration curve.

7 min

Expected Results

The curve should show a characteristic S-shape: slowly rising pH initially, a steep jump around the equivalence point (pH 7 for strong acid-strong base), then leveling off at high pH. The equivalence point volume should be approximately 25 mL.

Cleanup

Rinse the pH electrode and store in storage solution. Neutralize waste before disposal. Rinse all glassware.

Details

Category
Titrations
Difficulty
Intermediate (High School)
Duration
50 min
Est. Cost
$15.00
Steps
6
Materials
4

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Frequently Asked Questions

What is the objective of pH Titration Curve?
Record pH measurements during an acid-base titration and construct a complete S-shaped titration curve showing the equivalence point and buffer regions.
How difficult is pH Titration Curve?
This experiment is rated as Intermediate (High School). It takes approximately 50 minutes to complete.
What safety precautions are needed for pH Titration Curve?
Key safety precautions include: HCl and NaOH are corrosive; Wear safety goggles and gloves; Handle the pH electrode carefully — it is fragile.
What materials are needed for pH Titration Curve?
The main materials required are: Hydrochloric acid (HCl), Sodium hydroxide (NaOH), pH buffer solutions, Distilled water.
What results should I expect from pH Titration Curve?
The curve should show a characteristic S-shape: slowly rising pH initially, a steep jump around the equivalence point (pH 7 for strong acid-strong base), then leveling off at high pH. The equivalence point volume should be approximately 25 mL.