Conductometric titration is a type of titration that measures the change in the electrical conductivity of a solution as the reaction proceeds.
Basic Idea
- In any solution, ions conduct electricity.
- During a chemical reaction (like acid-base or precipitation), the number and type of ions in the solution change.
- By measuring the conductivity, we can detect when the reaction is complete (the equivalence point).
How It Works
- Set-up:
- You have a solution of one reactant (like an acid) in a vessel.
- Electrodes are placed in the solution to measure conductivity.
- The other reactant (like a base) is added gradually from a burette.
- Reaction Progress:
- As the titrant is added, the ions in the solution either increase, decrease, or change type, which affects conductivity.
- Example: In the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH):
- HCl has H⁺ and Cl⁻ ions.
- NaOH has Na⁺ and OH⁻ ions.
- As OH⁻ neutralizes H⁺ to form water, the number of highly mobile H⁺ ions decreases, so conductivity decreases.
- Detecting the Endpoint:
- Conductivity is continuously measured.
- The equivalence point is identified where the conductivity shows a sudden change (either a minimum or maximum depending on the type of reaction).
Key Points
- Conductometric titration does not need indicators.
- It is especially useful when:
- The reaction does not have a color change.
- The solution is colored or opaque.
- Works well for:
- Acid-base titrations
- Precipitation titrations
- Complexometric titrations
Example Patterns
- Strong Acid + Strong Base:
- Conductivity decreases to a minimum at the equivalence point, then slightly increases after excess base is added.
- Weak Acid + Strong Base:
- Conductivity gradually decreases, then increases sharply after equivalence.