Required Practical 2

Aim

To determine the reacting volumes of solutions of a strong acid and a strong alkali by titration.

Materials Needed

• Strong acid solution (e.g., hydrochloric acid)
• Strong alkali solution (e.g., sodium hydroxide)
• Burette
• Burette stand
• Pipette
• Pipette filler
• Conical flask
• Phenolphthalein indicator (optional)
• Distilled water (for rinsing equipment)
• White tile or piece of paper (for colour changes)

Safety Precautions

• Eye Protection: Wear safety goggles or protective eyewear to shield your eyes from any accidental splashes or spills of the acid or alkali solutions.
• Lab Coat or Apron: Wear a lab coat or apron to protect your clothing from potential spills or splashes of the solutions.
• Proper Ventilation: Perform the titration in a well-ventilated area or under a fume hood to avoid inhaling any fumes or vapours from the solutions.
• Dilute Acid: Use dilute solutions of the strong acid and alkali, as concentrated solutions can be corrosive and cause severe burns.
• Handling Acid and Alkali: Handle the acid and alkali solutions with care and avoid contact with your skin. If accidental spills occur, rinse immediately with plenty of water.
• Burette Handling: Handle the burette with care to prevent it from slipping or breaking. Secure the burette firmly in the burette stand.
• Avoid ContaminationIntroduction of modern DNA into ancient samples, which can interfere with genetic analysis and lead to inaccurate conclusions.: Ensure all equipment, including the conical flask and pipette, are clean and free from any residual substances before starting the titration.
• Add Alkali Slowly: Near the endpoint, add the alkali solution slowly and dropwise to avoid overshooting the endpoint, which could lead to inaccurate results.
• Glassware Safety: Check all glassware for cracks or chips before use. Discard any damaged glassware to prevent potential accidents.
• Proper Disposal: Dispose of the waste solutions properly according to your school or laboratory's guidelines for chemical waste disposal.
• Read MSDS: Familiarise yourself with the Material Safety Data Sheets (MSDS) for the acid and alkali solutions to understand their hazards and handling procedures.
• Do Not Taste: Never taste or ingest any of the solutions, as they may be harmful or toxic.

Procedure

1. Prepare the Solutions
   1. Using a pipette, accurately measure a known volume of the strong acid solution (e.g., 25.00 mL) and transfer it to a clean conical flask. If using phenolphthalein indicator, add a few drops to the acid solution.
2. Set Up the Burette
   1. Rinse the burette with a small amount of the strong alkali solution to ensure it is clean. Fill the burette with the strong alkali solution, making sure there are no air bubbles in the tip.
3. Perform the Titration
   1. Add the strong alkali solution from the burette to the acid solution in the conical flask, drop by drop, swirling the flask after each addition. As the alkali is added, the acid will neutralise, and the solution will change colour if using phenolphthalein indicator.
4. Endpoint Detection
   1. As you get close to the endpoint (the point where the acid has been completely neutralised by the alkali), add the alkali solution more cautiously and dropwise to avoid overshooting the endpoint. The endpoint is reached when the colour change is permanent.
5. Record the Burette Reading
   1. Note the initial and final burette readings to determine the volume of the strong alkali solution used to neutralise the acid.
6. Repeat the Titration
   1. Perform at least two more titrations to ensure accuracy and consistency in your results.
7. Calculate the Average Volume
   1. Calculate the average volume of the strong alkali solution used to neutralise the acid by adding the volumes used in each titration and dividing by the number of titrations.
8. Calculate the Concentration of the Alkali
   1. Using the known concentration of the strong acid solution (e.g., 0.1 mol/dm³) and the average volume of the alkali used in the titrations, calculate the concentration of the alkali solution in mol/dm³ using the equation:
   2. Concentration of alkali (mol/dm³) = Concentration of acid (mol/dm³) x Volume of acid (dm³) / Volume of alkali (dm³)
9. Convert Concentration to g/dm³
   1. If needed, convert the concentration of the alkali solution from mol/dm³ to g/dm³ using the molar mass of the alkali.

Conclusion

By following this procedure, you can successfully determine the reacting volumes of solutions of a strong acid and a strong alkali through titration. Additionally, you can calculate the concentration of one of the solutions in mol/dm³ and g/dm³ using the known concentration of the other solution and the reacting volumes obtained from the titration. Always ensure accurate measurements and proper techniques are used to obtain reliable results.