Search results
Results from the WOW.Com Content Network
Phenolphthalein is slightly soluble in water and usually is dissolved in alcohols in experiments. It is a weak acid, which can lose H + ions in solution. The nonionized phenolphthalein molecule is colorless and the double deprotonated phenolphthalein ion is fuchsia. Further proton loss in higher pH occurs slowly and leads to a colorless form.
Upon reduction, the very intense pink color of the cationic form of phenolphthalein fades to a faint yellow color. It is this form of phenolphthalein that is present in Kastle–Meyer test kits. In order to generate the intense pink color indicative of a positive test, the reduced phenolphthalein must be oxidized back to its normal, colored form.
Solution: The main components of a universal indicator, in the form of a solution, are thymol blue, methyl red, bromothymol blue, and phenolphthalein. This mixture is important because each component loses or gains protons depending upon the acidity or alkalinity of the solution being tested. It is beneficial to use this type of universal ...
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.
For optimal accuracy, the color difference between the two species should be as clear as possible, and the narrower the pH range of the color change the better. In some indicators, such as phenolphthalein, one of the species is colorless, whereas in other indicators, such as methyl red, both species confer a color. While pH indicators work ...
Ferroxyl indicator, or rust indicator, is a solution containing potassium hexacyanoferrate(III), phenolphthalein and sodium chloride. It turns blue in the presence of Fe 2+ ions, and pink in the presence of hydroxide (OH −) ions. It can be used to detect metal oxidation, and is often used to detect rusting in various situations.
Bromothymol blue (also known as bromothymol sulfone phthalein and BTB) is a pH indicator.It is mostly used in applications that require measuring substances that would have a relatively neutral pH (near 7).
Acid-base titrations and redox titrations are often performed in which common indicators are used to locate the end point e.g., methyl orange, phenolphthalein for acid base titrations and starch solutions for iodometric type redox process. However, electrical conductance measurements can also be used as a tool to locate the end point.