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EEJ MAIN Chemistry QUESTION #7114
Question 1
When titrating a weak base against a strong acid, which indicator and end-point color change is the most appropriate?
  • Methyl orange; Yellow to pinkish red✔️
  • Phenolphthalein; Pink to colourless
  • Methyl orange; Colourless to pink
  • Phenolphthalein; Pinkish red to yellow
Correct Answer Explanation
For a titration between a weak base and a strong acid, the equivalence point lies in the acidic range ($pH < 7$). Methyl orange is a suitable indicator as its color change interval ($3.1$ to $4.4$) matches this range, changing from yellow in basic/neutral conditions to pinkish-red in acidic conditions.