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Which indicator should be used and why?

First think about what will be reacting in the titration. The NaOH will react in an acid-base reaction with the carboxylic acid. As the carboxylic acid is a weak acid, and NaOH is a strong base, you would get a titration curve like the one attached.

So you need the indicator which changes colour in the range of the straight line section which is phenolphthalein. Hope this helps!
Reply 2
Original post by clo-jo11
First think about what will be reacting in the titration. The NaOH will react in an acid-base reaction with the carboxylic acid. As the carboxylic acid is a weak acid, and NaOH is a strong base, you would get a titration curve like the one attached.

So you need the indicator which changes colour in the range of the straight line section which is phenolphthalein. Hope this helps!


But isn't it HCl and NaOH?
Original post by Adorable98
But isn't it HCl and NaOH?


And this is why I'm failing all my exams because I can't read questions :s-smilie:
The only thing I can think of is the titre value is the amount needed to neutralise the HCl and carboxylic acid but I'm not sure about the indicator if that's the case, sorry.
Reply 4
Bump .. :frown:
Original post by Adorable98
Bump .. :frown:


It is a mixture of a weak and a strong acid.

Phenolphthalein can be used for strong base-weak acid and strong base-strong acid titrations.
Reply 6
Original post by charco
It is a mixture of a weak and a strong acid.

Phenolphthalein can be used for strong base-weak acid and strong base-strong acid titrations.


I see, so it doesn't matter whether the acid is strong or weak, if a strong base is present we'd always use Phenolphthalein,
thank you!!

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