SURAT CHEMICAL TAG::
Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions. ... It is a weak acid, which can lose H+ ions in solution.
Question: How to make phenolphthalein TEST solution?
Ans: Dissolve 10.0 g of phenolphthalein powder in 750 mL of ethanol and dilute to 1 L with distilled water. Add 0.1 N sodium hydroxide (NaOH) solution dropwise to the first permanent faint pink end point. Color and pH range: colorless 8.3-10.0 red.
A strong acid- strong base titration is performed using a phenolphthalein indicator. Phenolphtalein is chosen because it changes color in a pH range between 8.3 – 10. It will appear pink in basic solutions and clear in acidic solutions.
Phenolphthalein, (C20H14O4), an organic compound of the phthalein family that is widely employed as an acid-base indicator. As an indicator of a solution's pH, phenolphthalein is colourless below pH 8.5 and attains a pink to deep red hue above pH 9.0.
Phenolphthalein is a colourless, weak acid which dissociates in water forming pink anions. Under acidic conditions, the equilibrium is to the left,and the concentration of the anions is too low for the pink colour to be observed.
Phenolphthalein is basic indicator which remain colorless in acidic and neutral solution and turns pink or magenta in basic solution. If few drops of NaOH is added again to the same solution, the solution become basic and the pink color of the phenolphthalein reappears.