Acid-base titration is a type of titration in which an acid reacts with a base to determine the unknown concentration of one of the solutions. It is one of the most common types of titrations.
Basic Idea
- An acid and a base react in a neutralization reaction to form water and a salt.
- By carefully adding a solution of known concentration (titrant) to the solution of unknown concentration until neutralization occurs, we can calculate the unknown concentration.
How It Works
- Setup:
- A solution of unknown concentration (acid or base) is placed in a conical flask.
- A burette is filled with the titrant (solution of known concentration).
- A few drops of indicator (like phenolphthalein or methyl orange) are added to detect the endpoint.
- Titration Process:
- The titrant is added slowly while swirling the flask.
- The indicator changes color when the reaction is complete (neutralization).
- Endpoint Detection:
- The endpoint is when the indicator shows a color change.
- The volume of titrant used is recorded.
- Calculation:
- Using the stoichiometry of the reaction and the volume of titrant added, the unknown concentration can be calculated.
Example Reactions
- Strong acid + Strong base:
HCl + NaOH → NaCl + H₂O- Indicator: Phenolphthalein (colorless → pink at endpoint)
- Weak acid + Strong base:
CH₃COOH + NaOH → CH₃COONa + H₂O- Endpoint is reached slightly after neutralization; phenolphthalein is preferred.
- Strong acid + Weak base:
HCl + NH₃ → NH₄Cl- Endpoint is acidic; methyl orange is preferred.
Applications
- Determining the concentration of acids or bases in solutions.
- Used in pharmaceutical, chemical, and food industries.
- Monitoring water quality by measuring acidity or alkalinity.