Class 11 Chemistry - Acid-Base Titration

Aim

To determine the concentration of a given solution of an acid or base by titration, and to understand the process of neutralization through volumetric analysis.

Materials Required

• Hydrochloric acid (HCl)
• Sodium hydroxide (NaOH)
• Phenolphthalein indicator (for detecting the endpoint)
• Burette
• Pipette
• Conical flask
• White tile (to see the color change clearly)

Image Reference

Procedure

1. Fill the burette with the sodium hydroxide (NaOH) solution. Ensure there are no air bubbles in the burette and that the initial volume is recorded accurately.
2. Take a known volume (usually 25 mL) of hydrochloric acid (HCl) in a clean conical flask using a pipette. Add 2-3 drops of phenolphthalein indicator to the flask. The solution will remain colorless in acidic conditions.
3. Place the conical flask on a white tile beneath the burette to better observe the color change during titration.
4. Gradually add NaOH from the burette into the conical flask containing HCl while continuously swirling the flask. The base will react with the acid to neutralize it.
5. As the titration proceeds, the color of the solution will change. When the pink color stays for about 30 seconds, this indicates that the endpoint has been reached, signifying complete neutralization of the acid by the base.
6. Record the final volume of NaOH used and calculate the amount of NaOH required to neutralize the given amount of HCl.

Observation

The amount of NaOH required to neutralize the given amount of HCl indicates the concentration of the acid. The endpoint of the titration is marked by a permanent color change from colorless to a faint pink, indicating that the acid has been completely neutralized.

Reaction Equation

The neutralization reaction between hydrochloric acid and sodium hydroxide is:

HCl + NaOH → NaCl + H2O

Precautions

• Ensure that the burette is filled properly without any air bubbles to get accurate readings.
• Do not add NaOH too quickly, as it may overshoot the endpoint.
• Always note the initial and final readings of the burette accurately.
• Use a white tile to help observe the color change more clearly.
• Perform the titration in a well-ventilated area and wear safety goggles and gloves to handle the chemicals safely.

Video Reference