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Phenolphthalein (/ f ɛ ˈ n ɒ l (f) θ ə l iː n / [citation needed] feh-NOL(F)-thə-leen) is a chemical compound with the formula C 20 H 14 O 4 and is often written as "HIn", "HPh", "phph" or simply "Ph" in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations.
Normally, the indicator causes the color of the solution to change depending on the pH. Indicators can also show change in other physical properties; for example, olfactory indicators show change in their odor. The pH value of a neutral solution is 7.0 at 25°C (standard laboratory conditions). Solutions with a pH value below 7.0 are considered ...
Paper form: It is a strip of coloured paper which changes colour to red if the solution is acidic and to blue, if the solution is basic. The strip can be placed directly onto a surface of a wet substance or a few drops of the solution can be dropped onto the universal indicator using dropping equipment.
An acid-base indicator (e.g., phenolphthalein) changes color depending on the pH. Redox indicators are also frequently used. A drop of indicator solution is added to the titration at the start; when the color changes the endpoint has been reached, this is an approximation of the equivalence point. Conductance
Its sharp and easily detectable colour changes makes phenolphthalein a valuable tool for determining the endpoint of acid-base titrations, as a precise pH change signifies the completion of the reaction. When a weak acid reacts with a weak base, the equivalence point solution will be basic if the base is stronger and acidic if the acid is stronger.
Animation of a strong acid–strong base neutralization titration (using phenolphthalein). The equivalence point is marked in red. The equivalence point is marked in red. In chemistry, neutralization or neutralisation (see spelling differences ) is a chemical reaction in which acid and a base react with an equivalent quantity of each other.
The main use of litmus is to test whether a solution is acidic or basic, as blue litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple. [2]
The total acid number (TAN) is a measurement of acidity that is determined by the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. [1] It is an important quality measurement of crude oil. The TAN value indicates to the crude oil refinery the potential of corrosion problems.