Chemistry

Problem

A student titrates 25.0 mL of 0.100 M acetic acid (

pK_a = 4.76

) with 0.100 M NaOH while using phenolphthalein as the indicator (

pK_a = 9.3

, colorless when protonated, pink when deprotonated). At approximately which volume of NaOH added will the solution first develop a faint permanent pink color? a) Between

24\,\text{mL}

and

25\,\text{mL}

of NaOH b) At exactly

25.0\,\text{mL}

of NaOH c) Between

25.0\,\text{mL}

and

25.1\,\text{mL}

of NaOH d) After more than

30\,\text{mL}

of NaOH

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