Question

Bromophenol blue is another common acid-base indicator which changes color from yellow in acidic solution to blue in basic solution. The pH values for this indicator are in a range of approximately 3.0 to 4.6. Instead of using phenolphthalein in the CH3COOH-NaOH titration, if bromophenol blue was used, would the calculated molarity of acetic acid be higher, lower, or the same? Explain.

Answer 1

It would be higher

Step-by-step explanation:

If bromophenol blue was used instead of phenolphthalein in the CH3COOH-NaOH titration, the calculated molarity of acetic acid would be higher. This is because the pH range for bromophenol blue is lower than that of phenolphthalein (approximately 3.0 to 4.6 compared to 8.2 to 10.0). Therefore, the endpoint of the titration (where the indicator changes color) would occur at a lower pH for bromophenol blue, indicating that more NaOH has been added to neutralize the acetic acid. This would result in a higher calculated molarity of acetic acid.