September 20, 2021, 09:24:21 AM
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Topic: Why does adding too much indicator alter titration results.?  (Read 281 times)

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Offline Sam1988

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Why does adding too much indicator alter titration results.?
« on: April 29, 2021, 01:00:15 AM »
Why does adding too much indicator alter titration results.?
I’ve read that adding a weak acid indicator to a base will remove OH-and mean less acid is required to neutralise the base.

But surely, even if a large amount of indicator is added, the H+ from the indicator consumes some OH- and thus drives the indicator into its alkaline form. 

Now as  H+ from the acid in the burett is added during a titration, the remaining OH- in the base is consumed . Also the equivalent amount of alkaline indicator formed by adding the indicator to the base in the first place will surely be converted back to the acidic form because of the acid being added.

If that didn’t happen, the indicator would remain in its alkaline form and not change colour. 

So what I am saying is, I do not understand how the amount of indicator affects a titration?

I know in reality 2 drops has very small impact but what would happen if a much larger amount was added?
Are there any sums that can help explain what’s going on?

Offline Borek

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