why use phenolphthalein instead of methyl violet in a titration?
Please type your subject in the School Subject box. Any other words, including obscure abbreviations, are likely to delay responses from a teacher who knows that subject well.
normally, you want the titration to be end result of pH7. Crystal violet changes color at about 1.6, far from titrations.
wat the f
Phenolphthalein and methyl violet are both commonly used indicators in acid-base titrations, but they have different properties that make them suitable for different situations. Let me explain how to determine which indicator to use in a titration.
1. Understand the purpose of an indicator:
An indicator is a substance that changes color in response to changes in pH. It is added to the solution being titrated to visually indicate the endpoint of the reaction. The endpoint is the point at which the reactants have completely reacted, and the solution has reached neutrality or the desired pH value.
2. Consider the pH range of the titration:
Different acid-base titrations have different pH ranges. Phenolphthalein and methyl violet have different pH transition ranges where their color changes occur.
3. Properties of phenolphthalein:
Phenolphthalein is colorless in acidic solutions and turns pink or purple in the presence of a slightly basic to highly basic solution. Its pH transition range is approximately between pH 8.2 and 10.0. It is commonly used in strong acid-strong base titrations, where the endpoint is in the basic region.
4. Properties of methyl violet:
Methyl violet is blue or violet in acidic solutions and changes to yellow or colorless in the presence of a slightly acidic to neutral solution. Its pH transition range is around pH 0.0 to 1.6. Methyl violet is often used in weak acid-strong base titrations or for determining the endpoint of an acid titration when the acid is very weak and its initial concentration is low.
5. Choose the appropriate indicator:
Selecting the right indicator depends on the nature of the reactants and the desired pH range. If the titration involves a strong acid and strong base, phenolphthalein is commonly used because its pH transition range matches the endpoint of this type of titration. On the other hand, if you are performing a weak acid-strong base titration or the acid is weak and the initial concentration is low, methyl violet might be a better choice due to its suitable pH range.
In summary, the choice between phenolphthalein and methyl violet in a titration depends on the pH range of the reaction and the specific acid-base system being analyzed.