4. Acid-Base Reactions

Acid-Base Titrations

Acid-base titration can determine the concentrations of unknown acid or base solutions.

Setting up an Acid-Base Titration

An acid-base titration is an experimental procedure used to determined the unknown concentration of an acid or base by precisely neutralizing it with an acid or base of known concentration. This lets us quantitatively analyze the concentration of the unknown solution. Acid-base titrations can also be used to quantify the purity of chemicals.


Acid-base titration: The solution in the flask contains an unknown number of equivalents of base (or acid). The burette is calibrated to show volume to the nearest 0.001 cm3. It is filled with a solution of strong acid (or base) of known concentration. Small increments are added from the burette until, at the end point, one drop changes the indicator color permanently. (An indication of the approaching equivalence point is that the indicator changes color but changes back after stirring.) At the equivalence point, the total amount of acid (or base) is recorded from the burette readings. The number of equivalents of acid and base must be equal at the equivalence point.

Alkalimetry, or alkimetry, is the specialized analytic use of acid-base titration to determine the concentration of a basic (alkaline) substance; acidimetry, or acidometry, is the same concept applied to an acidic substance.

Materials for a Titration Procedure

  • burette
  • white tile (used to see a color change in the solution)
  • pipette
  • pH indicator (the type depends on the reactants )
  • Erlenmeyer or conical flask
  • titrant (a standard solution of known concentration; a common example is aqueous sodium carbonate)
  • analyte, or titrand (the solution of unknown concentration)

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