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What concentration is phenolphthalein indicator ? 1% or 0.1%
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Adam Kennedy Palfrey
What concentration is phenolphthalein indicator ? 1% or 0.1%
During titration of small amounts of acids, the molar amount of the indicator in 1-2 drops of $\pu{1 \%}$ indicator solution may not be negligible compared to the acid molar amount, affecting the result.
So for that cases, $\pu{0.1 \%}$ solution is used, to be able to dose smaller indicator amounts.
As the phenolphalein molar mass is about $M=\pu{318 g/mol}$, 1 drop of $\pu{1 \%}$ solution is equivalent about 3 drops of $\pu{0.01 M}\ \ce{NaOH}$.
During titration of small amounts of acids, the molar amount of the indicator in 1-2 drops of $\pu{1 \%}$ indicator solution may not be negligible compared to the acid molar amount, affecting the result.
So for that cases, $\pu{0.1 \%}$ solution is used, to be able to dose smaller indicator amounts.
As the phenolphalein molar mass is about $M=\pu{318 g/mol}$, 1 drop of $\pu{1 \%}$ solution is equivalent about 3 drops of $\pu{0.01 M}\ \ce{NaOH}$.
@VanThanhDo And so does mine. unless perhaps for rare exceptions, pH indicators are not used at so high concentration as 1%. By adding pH indicator, you add an acid or a base to the one you want to determine. Your interest is this addition should be negligible.More
Thank you a lot for your answer, even i dont understand well your explanation. All statements from other answers support for using phenolphalein indicator 0.1%. I really appreciated your help Poutnik.More
During titration of small amounts of acids, the molar amount of the indicator in 1-2 drops of $\pu{1 \%}$ indicator solution may not be negligible compared to the acid molar amount, affecting the result.
So for that cases, $\pu{0.1 \%}$ solution is used, to be able to dose smaller indicator amounts.
As the phenolphalein molar mass is about $M=\pu{318 g/mol}$, 1 drop of $\pu{1 \%}$ solution is equivalent about 3 drops of $\pu{0.01 M}\ \ce{NaOH}$.
During titration of small amounts of acids, the molar amount of the indicator in 1-2 drops of $\pu{1 \%}$ indicator solution may not be negligible compared to the acid molar amount, affecting the result.
So for that cases, $\pu{0.1 \%}$ solution is used, to be able to dose smaller indicator amounts.
As the phenolphalein molar mass is about $M=\pu{318 g/mol}$, 1 drop of $\pu{1 \%}$ solution is equivalent about 3 drops of $\pu{0.01 M}\ \ce{NaOH}$.
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