Making Salts from Acids and Alkalis: Titrations

Overview

• Titration is the process used to determine the volumes of acids and alkali solutions that react with each other using a suitable indicator.
• It is part of the GCSE Chemistry Single Science Curriculum under Chemical Changes.

Making Salts

• Salt Formation: A soluble salt is made by reacting an acid with an alkali (e.g., sodium hydroxide or ammonia).
• Steps:
  1. Conduct a titration to determine the correct volumes of acid and alkali.
  2. Mix the acid and alkali in the correct proportions without an indicator.
  3. Produce pure dry crystals through crystallisation.

Apparatus for Titration

• Pipette: Measures accurate volumes of a reactant.
• Burette: Adds measured volumes of one reactant to another.

Titration Method

1. Use pipette and filler to add a measured volume of sodium hydroxide to a conical flask.
2. Add a few drops of indicator and place the flask on a white tile.
3. Fill the burette with hydrochloric acid, note the starting volume.
4. Add acid gradually from the burette to the alkali, swirling to mix.
5. Stop when the indicator changes color permanently (the end-point).
6. Repeat until concordant titres are achieved.

Results

• Record results in a table.
• Example Table:
  • Rough: End Vol = 26.85 cm³, Start Vol = 1.00 cm³, Titre = 25.85 cm³
  • Run 1: End Vol = 24.60 cm³, Start Vol = 0.00 cm³, Titre = 24.60 cm³
  • Run 2: End Vol = 24.90 cm³, Start Vol = 0.60 cm³, Titre = 24.30 cm³
  • Run 3: End Vol = 24.00 cm³, Start Vol = 0.30 cm³, Titre = 24.70 cm³

Analysis

• At least two concordant titres (within 0.10 cm³) should be identified.
• Mean Titre Calculation:
  • Exclude non-concordant titres.
  • Example: Mean Titre = (24.60 + 24.70) / 2 = 24.65 cm³

Additional Resources

• Related Topics:

  • Reactions of metals
  • Acids, alkalis, and salts
  • Electrolysis
  • Sample exam questions on chemical changes

• External Links:

  • Chemistry exam practice
  • Jobs that use Chemistry
  • Royal Society of Chemistry

This guide provides the foundational steps and procedures for conducting titrations as part of GCSE Chemistry studies, focusing on the creation of salts from acids and alkalis.