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The graph below shows the change in pH of a reaction solution during a titration of 0.10 M NaOH with 0.10 M CH₃COOH - VCE - SSCE Chemistry - Question 4 - 2008 - Paper 1
Question 4
The graph below shows the change in pH of a reaction solution during a titration of 0.10 M NaOH with 0.10 M CH₃COOH. Titration of 20.00 mL 0.10 M NaOH with 0.10 M C... show full transcript
Worked Solution & Example Answer:The graph below shows the change in pH of a reaction solution during a titration of 0.10 M NaOH with 0.10 M CH₃COOH - VCE - SSCE Chemistry - Question 4 - 2008 - Paper 1
Step 1
A suitable indicator for the titration and the colour change observed is:
Answer
To determine the suitable indicator for this titration, we need to consider the pH range at which the indicator changes color. The titration of acetic acid (CH₃COOH) with sodium hydroxide (NaOH) typically results in a pH increase from around 4.75 (the pKa of acetic acid) to 9 or higher as you move towards the equivalence point.
Given the options of indicators:
- Methyl Red changes from red to yellow around a pH range of 4.4 to 6.2, which is too low for this titration.
- Phenolphthalein changes from colorless to pink/red in the pH range of approximately 8.2 to 10.0. This falls within the range of the expected pH at the equivalence point for this reaction.
Therefore, the correct answer is D. phenolphthalein, as it will undergo a visible change in color at the appropriate pH range during the titration.