Why are the results less accurate in a titration when too much indicator is added?

Question

For example, instead of adding two drops of indicator 20 are added...

Replying to Amy F, you are referring to the titrant, I am referring to the indicator.

actually nevermind... I think I know what you're trying to say

Answer 1

Alright, there are two reasons

1) when you add too much indicator to a titration, you are diluting the solution. Its just like if you were to add twenty drops of water to the solution, you would be changing the concentration. Changing the concentration means the titration might react differently, take much longer to complete, and the product will have a higher mass than what you would expect.

2) SOME BUT NOT ALL indicators react with their solution. Phenolphthalein is an example of a chemical that does not react, (don't ask me to go over the indicators that do react, eg: adding an acid to a base shows you have a base...). If your indicator does react with your solution, then the titration will be less successful. This reason really depends what your indicator is. Bromothymol Blue is an example of an indicator that reactis with acid.

Answer 2

An indicator should only be used to help you see the result of the actual experiment. 20 drops of indicator? Throw the experiment and start again!

Answer 3

It's possible for excessive indicator to consume a significant amount of the titrant.

Answer 4

I don't know, I'd guess because you're supposed to stop when it first starts to change and if it goes all the way you know you've gone too far and can throw out that experiment. Maybe with too much indicator it always goes all the way so it's harder to tell if you've added too much? Just a thought.