Acid-Base Titration with Methyl Orange

Titrating a weak base with a strong acid

Titrations Intermediate (High School) 40 min ~$12.00

Objective

Determine the concentration of a sodium carbonate solution by titrating it with hydrochloric acid using methyl orange indicator, suitable for acidic endpoints.

Background

Methyl orange changes color at pH 3.1-4.4 (red to yellow), making it suitable for titrations where the equivalence point is in the acidic range. Sodium carbonate reacts with HCl in a two-step process: first forming NaHCO₃, then NaCl + H₂O + CO₂. Methyl orange detects the second equivalence point.

Safety Warnings

  • HCl is corrosive — avoid skin contact
  • Wear safety goggles throughout
  • Methyl orange is an azo dye — avoid contact with skin

Required PPE

goggles lab_coat

Materials

  • Sodium carbonate (Na₂CO₃) (100 mL)
    Unknown concentration
  • Hydrochloric acid (HCl) (100 mL)
    0.1M standardized
  • Methyl orange indicator (5 mL)
    0.1% solution
  • Distilled water (200 mL)

Equipment

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette Pipette filler White tile

Procedure

1

Rinse the burette with HCl solution, then fill it to the 0 mL mark.

3 min
2

Pipette 25.0 mL of sodium carbonate solution into the Erlenmeyer flask.

2 min
3

Add 2-3 drops of methyl orange indicator. The solution should appear yellow (alkaline).

1 min
4

Add HCl slowly while swirling. Watch for the color change from yellow through orange.

8 min
5

Near the endpoint, add drop by drop until the solution changes from yellow to a persistent orange/salmon color.

5 min
6

Record the volume of HCl used. Repeat for concordant results.

15 min
7

Calculate the concentration of Na₂CO₃ considering the 1:2 stoichiometry (Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂).

5 min

Expected Results

The endpoint shows a clear transition from yellow to a persistent orange/salmon color. The volume ratio should confirm the 1:2 molar ratio of carbonate to acid.

Cleanup

Neutralize waste solutions. Rinse all glassware with distilled water. Drain and rinse the burette.

Details

Category
Titrations
Difficulty
Intermediate (High School)
Duration
40 min
Est. Cost
$12.00
Steps
7
Materials
4

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Frequently Asked Questions

What is the objective of Acid-Base Titration with Methyl Orange?
Determine the concentration of a sodium carbonate solution by titrating it with hydrochloric acid using methyl orange indicator, suitable for acidic endpoints.
How difficult is Acid-Base Titration with Methyl Orange?
This experiment is rated as Intermediate (High School). It takes approximately 40 minutes to complete.
What safety precautions are needed for Acid-Base Titration with Methyl Orange?
Key safety precautions include: HCl is corrosive — avoid skin contact; Wear safety goggles throughout; Methyl orange is an azo dye — avoid contact with skin.
What materials are needed for Acid-Base Titration with Methyl Orange?
The main materials required are: Sodium carbonate (Na₂CO₃), Hydrochloric acid (HCl), Methyl orange indicator, Distilled water.
What results should I expect from Acid-Base Titration with Methyl Orange?
The endpoint shows a clear transition from yellow to a persistent orange/salmon color. The volume ratio should confirm the 1:2 molar ratio of carbonate to acid.