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A titration was conducted by adding NaOH from a teflon-coated burette to HCl in a conical flask - HSC - SSCE Chemistry - Question 10 - 2005 - Paper 1
Question 10
A titration was conducted by adding NaOH from a teflon-coated burette to HCl in a conical flask. The pH in the flask was recorded during the titration and Curve A wa... show full transcript
Worked Solution & Example Answer:A titration was conducted by adding NaOH from a teflon-coated burette to HCl in a conical flask - HSC - SSCE Chemistry - Question 10 - 2005 - Paper 1
Step 1
What is the appropriate indicator for Curve B using the table?
Answer
To determine the appropriate indicator for Curve B, we need to analyze the characteristics of the titration being conducted. Based on the previous titration with HCl and NaOH that used bromothymol blue, we can infer that the second titration may involve a different type of acid.
Curve B indicates a different pH change behavior compared to Curve A, suggesting a stronger or weaker acid. By referring to the table provided:
- Methyl orange changes color at a pH between 3.1 to 4.4.
- Methyl red changes color between 4.4 to 6.2.
- Bromothymol blue changes color between 6.0 to 7.6.
- Cresolphtalein changes color from 8.1 to 9.7.
- Alizarin yellow changes color between 10.1 to 12.0.
Since Curve B appears to have a higher final pH, indicating a titration point consistent with the transition range of Cresolphtalein, the appropriate indicator for Curve B is therefore Cresolphtalein (C).