weakacidstrongbase

A weak acid strong base titration involves the reaction between a substance that donates protons only partially in solution and a substance that dissociates completely in solution, releasing hydroxide ions. When these two are mixed, a neutralization reaction occurs. The weak acid, for example, acetic acid (CH3COOH), reacts with the strong base, such as sodium hydroxide (NaOH). The general equation for this reaction is HA + OH- -> A- + H2O, where HA represents the weak acid and OH- represents the hydroxide ion from the strong base.

The equivalence point in such a titration is the point at which the moles of the added base exactly equal the initial moles of the weak acid. Because the conjugate base of a weak acid (A-) is itself a weak base, it will react with water to a small extent, producing hydroxide ions. This hydrolysis causes the solution at the equivalence point to be basic, meaning the pH will be greater than 7.

The titration curve for a weak acid strong base titration starts at a low pH due to the weak acid. As the strong base is added, the pH gradually increases. The buffer region is observed where the pH changes slowly as the weak acid is converted to its conjugate base. Beyond the equivalence point, the pH rises sharply as excess strong base is added, and the curve becomes relatively flat again. Indicators used for this titration should have a pH range that encompasses the sharp rise in pH around the equivalence point, typically a base-range indicator like phenolphthalein.