Titration is a technique to find an unknown concentration by adding one solution from a burette to a fixed volume of another until the reaction is just complete.
Malay: Pentitratan · Chinese: 滴定
Titration is a technique to find an unknown concentration by adding one solution from a burette to a fixed volume of another until the reaction is just complete. In acid–alkali titration, a pipette measures a fixed volume of one solution into a conical flask with a few drops of indicator, and the other solution is run in from the burette until the indicator changes colour at the end point.
A worked example shows the payoff. Suppose 25.0 cm³ of sodium hydroxide needs 20.0 cm³ of 0.10 mol dm⁻³ hydrochloric acid to reach the end point. From the balanced equation the acid and alkali react 1:1, so moles of acid = 0.10 × (20.0 ÷ 1000) = 0.0020 mol, which equals the moles of alkali. The molarity of the sodium hydroxide is then 0.0020 ÷ (25.0 ÷ 1000) = 0.08 mol dm⁻³. One accurate volume reading has delivered an unknown concentration.
The confusion to avoid is between titration, the whole technique, and the titre, which is just one number, the volume delivered from the burette in a single run. Another mix-up is which piece of apparatus does what: the pipette gives one fixed volume into the flask, while the burette gives the variable volume you read off. Swapping their roles in a description costs marks. Using distilled water to rinse the flask is fine, but rinsing the burette or pipette with water instead of the solution introduces an error.
Within this chapter titration ties molarity, standard solution and neutralisation together into one practical, and it is also the way soluble sodium, potassium and ammonium salts are prepared. Our teachers rehearse the full procedure with you until each reading is careful and repeatable.
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