Search results
Results from the WOW.Com Content Network
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 ...
A universal indicator is a pH indicator made of a solution of several compounds that exhibit various smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions. A universal indicator can be in paper form or present in a form of a solution.
Chemical structure of phenolphthalein, a common phthalein dye. Phthalein dyes are a class of dyes mainly used as pH indicators, due to their ability to change colors depending on pH. [1] They are formed by the reaction of phthalic anhydride with various phenols. They are a subclass of triarylmethane dyes. Common phthalein dyes include ...
Its popularity is because of its effectiveness in a broad pH range and its distinct colour transitions. [12] 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.
The equation for mass-balance in hydrogen ions can then be written as T H = [H +] + [A −][H +]/K a − K w / [H +] Titration curves for addition of a strong base to a weak acid with pK a of 4.85. The curves are labelled with the concentration of the acid. where K w represents the self-dissociation constant of water.
Indicator: A substance that changes color in response to a chemical change. An acid–base indicator (e.g., phenolphthalein) changes color depending on the pH. Redox indicators are also used. A drop of indicator solution is added to the titration at the beginning; the endpoint has been reached when the color changes.
An intermediate of the deprotonation mechanism is responsible for the greenish color in neutral solution. [ 2 ] The protonated form of bromothymol blue has its peak absorption at 427 nm thus transmitting yellow light in acidic solutions, while the deprotonated form has its peak absorption at 602 nm thus transmitting blue light in more basic ...