Appropriate indicators for the determination of end point in the titration of a weak acid with a strong base:


- Phenolphthalein is a commonly used indicator in acid-base titrations.
- It is colorless in acidic solutions and turns pink or magenta in basic solutions with a pH greater than 8.2.
- In the titration of a weak acid with a strong base, the equivalence point occurs when all the weak acid has reacted with the strong base, resulting in a basic solution.
- Therefore, phenolphthalein is suitable for this titration as it undergoes a noticeable color change around the equivalence point.


- Thymol blue is another indicator that can be used in acid-base titrations.
- It is yellow in acidic solutions and turns blue in basic solutions with a pH greater than 8.0.
- Similar to phenolphthalein, thymol blue can be used to determine the end point in the titration of a weak acid with a strong base.
- As the strong base is added to the weak acid, the pH of the solution gradually increases, and at the equivalence point, the solution becomes basic, causing thymol blue to change color.


- Bromophenol blue is not an appropriate indicator for the determination of the end point in the titration of a weak acid with a strong base.
- It is typically used in titrations involving weak bases or strong acids.
- Bromophenol blue changes color from yellow (acidic) to blue (basic) around pH 6.0.
- In the titration of a weak acid with a strong base, the pH at the equivalence point is higher than 6.0, so bromophenol blue would not provide a clear indication of the end point.


- Methyl orange is also not suitable for the determination of the end point in the titration of a weak acid with a strong base.
- It is commonly used in titrations involving strong acids and weak bases.
- Methyl orange changes color from red (acidic) to yellow (basic) around pH 4.4.
- In the titration of a weak acid with a strong base, the pH at the equivalence point is higher than 4.4, so methyl orange would not give an accurate indication of the end point.

Therefore, the appropriate indicators for the determination of the end point in the titration of a weak acid with a strong base are phenolphthalein and thymol blue. These indicators undergo noticeable color changes in the basic pH range, which is reached at the equivalence point of the titration.