Whether in an alkali (pink) or an acid (colorless) solution, the phenolphthalein indicator has one of two distinct structures. Both structures are light-absorbing in the ultraviolet spectrum, which the human eye cannot see. So it is challenging.
What is phenolphthalein?
- The phthalein family of chemical compounds includes the indicator phenolphthalein (C20H14O4). The powder is a thin, crystalline yellowish-white to light orange powder. It has a pKa of 9.3, is barely soluble in water, and, when dissolved in alcohol, is used as an indicator for acid-base titration investigations.
- It is colorless in liquid form until pH 8.5 when it transforms from pink to dark red. Adolf von Baeyer, a German chemist, created phenolphthalein in 1871. He produced it by fusing phenol and phthalic anhydride in the presence of sulfuric acid (H2SO4) or zinc chloride. Phenolphthalein is closely linked to the triphenylmethane dyes (ZnCl2).
- The abbreviation "HIn" or "php" in shorthand notation is frequently used to refer to the chemical compound phenolphthalein, which has the formula C20H14O4. Its structure consists of 2 alcoholic groups, one ketone group, three hexagonal structures, and one pentagonal structure. Another compound with carbon, hydrogen, and oxygen chain structure is phenolphthalein.
- Phenolphthalein is frequently used as an indicator in acid-base titrations. Due to its water solubility, phenolphthalein is frequently dissolved in alcohols before use in experiments. It is a weak acid that can lose H+ ions in solutions. While the ion of phenolphthalein is purple, the phenolphthalein molecule is colorless.
- A common indicator used in titration experiments to show the titration's endpoint is phenolphthalein, an inert, colorless acid. Since this molecule dissociates to generate pink anions when dissolved in water, the endpoint is signaled by the production of pink color.
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