Basics of titration
- Titration is a technique where a volume of solution of a known concentration is added to react with another solution to determine its concentration.
- The known solution (titrant) is added from a burette to a known quantity of the unknown solution (analyte) until reaction is complete. Thus, knowing the volume of titrant used allows us to determine the concentration of the analyte.
- An indicator that has a distinctive colour in an acidic or basic solution is used to signal the end of the reaction, which is also known as the endpoint or equivalence point.
- Usually, an equal number of moles of acid (H⁺) would react with an equal number of moles of base (OH^–) to fully neutralise the solution at the equivalence point.
Molarity of an acidic/basic solution
- The molarity of a solution is calculated by dividing the moles of solute by the volume of solution in litres or dm³.
- Thus, in a neutralisation reaction, the number of moles of acid reacted should be equal to the number of moles of base. Mathematically, we can represent this with this equation:

Solving questions on titration
- Sample question: If 25dm³ of sodium hydroxide solution is exactly neutralised by 1 mol/dm³ sulfuric acid, what is the volume of sulfuric acid used?
  - Firstly, we find the number of moles of sodium hydroxide
  - Next, we find the mole ratio of reactants using a balanced chemical equation. In this case, 2 moles of sodium hydroxide are fully neutralised by 1 mole of sulfuric acid.
  - Now, we find the volume of sulfuric acid used
- Sample question: 20.7 ml of 0.5 Molar sodium hydroxide is required to reach the end point when titrated against 15 ml of hydrochloric acid of unknown concentration. What is the concentration of acid?
  - We can also use the equation to solve questions like these, where the number of moles of acid equals the number of moles of base:
    
    (note: this equation only works for reactions with a one-to-one ratio between the acid and base)

3.03 - The Mole Concept (II)

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