Understanding Titrations

  • Titrations are a method of analysis used in chemistry to determine the concentration of an unknown solution by neutralising it with a solution of known concentration.
  • The solution of known concentration is referred to as the titrant while the solution of unknown concentration is known as the analyte.
  • The point of the titration where the reaction is complete and all the analyte has reacted with the titrant is called the equivalence point.
  • The end point is an indication, usually a colour change due to an indicator, which signals that the equivalence point has been reached.
  • It’s essential to understand that the end point and the equivalence point may not always coincide. This discrepancy is referred to as indicator error.

Process of a Titration

  • A titration process typically begins with the analyte placed in a flask along with a few drops of an indicator.
  • The titrant is then added from a burette into the flask containing the analyte and indicator until the end point is reached.
  • It is important to add the titrant slowly, especially as you approach the end point, to avoid overshooting the end point.
  • The volume of titrant used to reach the end point is measured and used to calculate the concentration of the analyte.

Calculations in Titrations

  • Moles of titrant can be calculated by multiplying the concentration (in mol/L) by the volume (in L) used in the titration.
  • The balanced chemical equation for the reaction taking place gives the mole ratio between the titrant and the analyte.
  • The mole ratio is used to calculate the moles, and subsequently the concentration, of the unknown analyte.

Indicators in Titrations

  • An indicator is a substance that changes colour at or near the equivalence point of the titration.
  • The choice of indicator depends on the nature of the reaction. Phenolphthalein is commonly used in acid-base titrations where it turns from pink to colourless as the solution becomes acidic.
  • Some titrations might not require an indicator, if the reaction itself produces a visible change, these are called self-indicating reactions.

Remember to practice titration calculations to help solidify your understanding. Always refer to the balanced chemical equation for the reaction to determine the mole ratio between the reactants. And finally, while performing a titration, always ensure to add the titrant slowly to avoid overshooting the end point.