Safety, disposal of waste, and storageĬitric acid is a relatively strong weak acid, but no special precautions are required for its use. This phenomenon makes these titrations very easy to perform, and therefore very suitable for novices. The result is that as the equivalence point is approached, even with swirling, the pink-red colour appears where the drops of titrant enter the titration flask and persists, at first for fractions of a second, then longer and longer, until a faint pink colour can be seen throughout the solution that persists for at least one minute (see Question 3). In comparison to titrations with a strong acid such as hydrochloric acid, the diluted weak acid “mops up” the base in the drops of added titrant more slowly. Phenolphthalein indicator is an excellent choice for this titration, changing from colourless to pink to red. From about one added drop of the 0.1 M NaOH solution before the equivalence point of the titration to about one added drop after the equivalence point the pH of the titration solution climbs extremely steeply from slightly below 7 to above 9.Ī visual acid-base indicator chosen for the titration must change from its acid colour to its base colour in the range 7 to 9. When titrated by a strong base such as 0.1 M NaOH solution, a solution of citric acid traverses a buffer region during which the pH of the solution climbs gradually then more steeply. 3 Titrating citric acid against strong base Citric acid can be purchased at low cost as a reagent chemical of either form at various purity levels, 2 or at even lower cost as a consumer substance of unspecified purity and usually unspecified form. Both solids are stable and remain free-flowing in the bottle after many years of storage. The solid monohydrate loses water below 100 ☌ when heated, forming the anhydrous solid, which melts at 156 ☌, and decomposes at 175 ☌. It is produced as a crystalline solid, either anhydrous, or as a monohydrate, and is available in either form at low cost. Citric acidĬitric acid 1 is produced by the fermentation of sugars (> 1 M tonne per year) for use in beverages and foods (70%) in detergents (20%) and in cosmetics, pharmaceuticals and other chemicals (10%). A second article will suggest applications of the same experiment that are suitable for experienced titrators. ![]() This article presents a neutralization titration of a citric acid solution by sodium hydroxide solution in a format suitable for beginner titrators. For inexperienced students its titrations against strong base are easier to perform. In comparison to using hydro-chloric acid solutions, using solid citric acid and its solutions in water is safer and more convenient. ![]() Citric acid is a user-friendly, inexpensive, water-soluble, crystalline solid carboxylic acid.
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