Question
Andrea is performing an experiment in which she needs to know when a strong acid is present. She is not sure which indicator to use, so she looks up the following table in her science textbook.
Indicator pH range
thymol Blue 1.2 - 2.8
phenol Red 6.4 - 8.0
phenolphthalein 8.0 - 10.0
trinitrobenzoic acid 12.0 - 13.4
According to the textbook, which indicator should Andrea use?
Hint: Neutral substances have a pH of 7. Acids have a pH that is less than 7, and bases have a pH that is greater than 7.
A.
trinitrobenzoic acid
B.
phenol Red
C.
thymol Blue
D.
phenolphthalein
Indicator pH range
thymol Blue 1.2 - 2.8
phenol Red 6.4 - 8.0
phenolphthalein 8.0 - 10.0
trinitrobenzoic acid 12.0 - 13.4
According to the textbook, which indicator should Andrea use?
Hint: Neutral substances have a pH of 7. Acids have a pH that is less than 7, and bases have a pH that is greater than 7.
A.
trinitrobenzoic acid
B.
phenol Red
C.
thymol Blue
D.
phenolphthalein
Answers
GPT-4o mini
Since Andrea is looking for an indicator that can detect a strong acid, she should choose one that has a pH range that includes values less than 7.
From the table:
- Thymol Blue has a pH range of 1.2 - 2.8 (suitable for strong acids)
- Phenol Red has a pH range of 6.4 - 8.0 (not suitable for strong acids)
- Phenolphthalein has a pH range of 8.0 - 10.0 (not suitable for strong acids)
- Trinitrobenzoic acid has a pH range of 12.0 - 13.4 (not suitable for strong acids)
Therefore, the best choice for detecting a strong acid is:
**C. thymol Blue**
From the table:
- Thymol Blue has a pH range of 1.2 - 2.8 (suitable for strong acids)
- Phenol Red has a pH range of 6.4 - 8.0 (not suitable for strong acids)
- Phenolphthalein has a pH range of 8.0 - 10.0 (not suitable for strong acids)
- Trinitrobenzoic acid has a pH range of 12.0 - 13.4 (not suitable for strong acids)
Therefore, the best choice for detecting a strong acid is:
**C. thymol Blue**
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