To detect the presence of a strong acid, Andrea needs an indicator that changes color at a low pH, which corresponds to acidic conditions.
From the table provided:
- Thymol Blue has a pH range of 1.2 - 2.8, making it suitable for detecting strong acids.
- Phenol Red (pH range 6.4 - 8.0) is for neutral to slightly basic conditions.
- Phenolphthalein (pH range 8.0 - 10.0) is for basic conditions.
- Trinitrobenzoic acid (pH range 12.0 - 13.4) is for very basic conditions.
Given this information, Andrea should use D. thymol Blue, as it is suitable for detecting strong acids with a pH range well below 7.