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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: student78 on October 09, 2007, 01:27:58 PM

Title: What indicator to use for a titration of aspirin solution with NaOH solution?
Post by: student78 on October 09, 2007, 01:27:58 PM

I have some praticals at school the other day to do with determening of the pKa values of methyl orange, phenolphthalein and aspirin. The teacher tried to explain the following question to use, but his answer made no sense to me. In the end he wasnt sure what the answer was.

Question: What would be a good indicator (methyl orange or phenolphthalein) to use for a titration of aspirin with 0.1M NaOH solution?

Any help would be greatly appreciated

Many thanks

Title: Re: What indicator to use for a titration of aspirin solution with NaOH solution?
Post by: Borek on October 09, 2007, 01:36:42 PM

What will be endpoint pH for aspirin titration?

Title: Re: What indicator to use for a titration of aspirin solution with NaOH solution
Post by: student78 on October 09, 2007, 02:32:15 PM

It was between 10 and 11.5 for me.
I think its 11.11

Title: Re: What indicator to use for a titration of aspirin solution with NaOH solution?
Post by: Borek on October 09, 2007, 03:07:48 PM

Which indicator changes color closee to this pH?

Title: Re: What indicator to use for a titration of aspirin solution with NaOH solution
Post by: student78 on October 09, 2007, 03:14:08 PM

For phenolphthalein its 10.06 and for methyl orange its 8.60.

Title: Re: What indicator to use for a titration of aspirin solution with NaOH solution?
Post by: Borek on October 09, 2007, 04:03:33 PM

Select the one that is closer to the endpoint and you are ready.

Title: Re: What indicator to use for a titration of aspirin solution with NaOH solution
Post by: student78 on October 10, 2007, 05:14:55 PM

Is there some sort of full explanation which i can use?

many thnks