Question

Assess the suitability of methy orange to signal the equivalent point of sodium hydroxide and acetic acid. Use PH range over which methy orange change color, if conclude that methyl orange is not a reliable indicator,suggest an alternate indicator which would be more accurate

Answer 1

For the titration of acetic acid (weak acid) and NaOH( STRONG BASE), the equivalence point occurs, not at pH 7.

for example, titration of 0.1M acetic acid and 0.1M NaOH give an equivalence point at about 8.7.

Since sodium acetate ( salt) is hydrolysed.

In general, the rapid [H change for equivalence point of weak acid and strong base IS FROM (6.5-10).

Since methyl orange has range of (3.1-4.4), this cannot be used here as an indicator.

But PHENOLPHTHALEIN can be used HERE AS AN INDICATOR instead of methylorange, BECAUSE phenolphthalein pH range is (8-9.5). Below 8 it is colorless and above 9.5 it is pink in color.

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