In an oxalic acid (a weak acid) and sodium hydroxide (a strong base) neutralization reaction, a suitable indicator to use would be phenolphthalein.
Reason for Using Phenolphthalein:
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pH Range: Phenolphthalein changes color around a pH range of 8.2 to 10.0, which is suitable because the equivalence point of the neutralization reaction between a weak acid (oxalic acid) and a strong base (sodium hydroxide) occurs at a pH greater than 7 (typically around pH 8 to 9).
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Color Change: In acidic solutions, phenolphthalein is colorless, and in basic solutions, it turns pink. This color change provides a clear visual indication of the endpoint of the titration.
Reason for Not Using Other Indicators:
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Methyl Orange: This indicator changes color in the range of pH 3.1 to 4.4, which is more suited for strong acid and weak base titrations and would not reflect the equivalence point accurately in this case.
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Bromothymol Blue: It has a range of pH 6.0 to 7.6, which is too low for the endpoint of this reaction.
Therefore, phenolphthalein is the most appropriate indicator for monitoring the progress of the neutralization reaction between oxalic acid and sodium hydroxide.