Acid-Base Titration

Acid-Base Titration

• A neutralization reaction is a reaction between an acid and a base.
• The general equation for a neutralization reaction is: acid + base → salt + water.
• Example: HCl(aq) + KOH(aq) → HOH(l) + KCl(aq)

Titration

• Titration is a common method of quantitative chemical analysis.
• It's used to determine the concentration of a substance in a solution.

Titration Terminology

• Burette: A device used for dispensing specific amounts of a chemical solution.
• Standard Solution: A solution with a known concentration.
• Titrant: The solution in the burette during a titration.
• Equivalence Point: The point during titration when neutralization is complete.
• Endpoint: The point during titration where a sharp change in solution color occurs.
• Indicator: A substance that changes color at the endpoint to show when the reaction between two chemicals is complete.

Steps for Titrating

• A known volume of the sample is transferred into a flask. The concentration of this solution is unknown.
• A few drops of indicator are added to the solution in the flask.
• The burette is filled with the known concentration solution (standard solution).
• The solution in the burette is called the titrant.
• An initial burette volume reading is taken.
• The titrant is added drop by drop to the sample in the flask.
• The titrant is added until the reaction is judged complete or the neutralization is complete, reaching the equivalence point.
• The indicator in the flask will change color at this point (endpoint).
• At the endpoint, no more titrant is added.
• The volume of titrant used (final burette reading) is recorded.
• This information is used to calculate the concentration of the solution in the flask.
• At least 3 trials are performed during a titration to improve the reliability of the results (i.e., for calculating concentration).

Indicators

• Indicators change color depending on whether the solution is acidic or basic, crucial for determining the endpoint in a titration.
• Examples include: Litmus, Methyl orange, Bromothymol blue, Phenolphthalein. Litmus changes from red to blue in basic solution; methyl orange from red to yellow. Bromothymol blue changes from yellow to green in a basic solution; phenolphthalein changes from colorless to red.

Practice Problems

• Practice problems include calculating the concentration of HCl using titration with NaOH, and calculating the concentration of hydrochloric acid using sodium carbonate. Data tables provide the specific readings needed for these calculations.