Acid-Base Titration Experiment Objective
To determine the concentration of an unknown acid or base using a standard solution, a burette, and an indicator, while exploring neutralization reactions and stoichiometry.
Acid-base titration experiment Materials Required
- Burette (50 mL)
- Conical flask (250 mL)
- Clamp stand
- Pipette (25 mL) and pipette filler
- Beaker (100 mL)
- Funnel
- Distilled water
- Standard sodium hydroxide solution (NaOH)
- Hydrochloric acid (HCl) of unknown concentration
- Phenolphthalein or methyl orange indicator
Procedure
Setup the Apparatus:
- Attach the burette vertically to the clamp stand.
- Rinse the burette with distilled water, then rinse it with a small amount of the sodium hydroxide solution. Fill the burette with NaOH solution using a funnel and remove the funnel afterward to prevent dripping.
- Ensure no air bubbles are present in the burette tip and record the initial reading.
Prepare the Acid Solution:
- Rinse the pipette with distilled water, then with a small amount of hydrochloric acid. Use the pipette to transfer 25 mL of the HCl solution into the conical flask.
- Add 2–3 drops of phenolphthalein (or methyl orange) indicator to the acid solution in the flask.
Titration Process:
- Place the conical flask beneath the burette, ensuring the tip of the burette is above the flask but not submerged.
- Slowly release the NaOH solution into the acid while swirling the conical flask gently to mix.
- As you approach the endpoint (color change), add the base dropwise to avoid overshooting the equivalence point.
Determine the Endpoint:
- For phenolphthalein: The solution changes from colorless to faint pink at the endpoint.
- For methyl orange: The solution changes from red to orange/yellow at the endpoint.
- Record the final reading on the burette.
Repeat for Accuracy:
- Repeat the titration at least three times to obtain consistent readings.
Observations and Calculations
Record Readings:
- Note the initial and final burette readings for each trial. Calculate the volume of NaOH used (titre value).
Calculate the Concentration:
- Use the neutralization equation: NaOH+HCl→NaCl+H2ONaOH + HCl → NaCl + H_2ONaOH+HCl→NaCl+H2O
- Using the formula: C1V1=C2V2C_1V_1 = C_2V_2C1V1=C2V2 Where:
- C1C_1C1 = Concentration of the HCl (unknown)
- V1V_1V1 = Volume of HCl (25 mL)
- C2C_2C2 = Concentration of NaOH (known)
- V2V_2V2 = Volume of NaOH used (titre value)
Average Titre Value:
- Calculate the average titre from consistent readings and use it to find the unknown concentration.
Safety Notes
- Wear gloves and goggles throughout acid-base titration experiment.
- Handle acids and bases with care to avoid spills.
- Dispose of waste solutions according to laboratory safety guidelines.
Applications
acid-base titration experiment is widely used in chemistry to determine the unknown concentration of acids or bases. It’s a foundational technique for studying reaction stoichiometry, pH changes, and neutralization.