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Titrations help?

ok so guys i have this titration experiment exam tomorrow and im really struggling with these last questions, i can't seem to find the answer anywhere so if you know the answer pls pls pls pls answer it i will be soooo grateful,

1) why are concordant results used to find the mean titre ?
2) explain why it id important to rinse out the conical flask and pippete with a regeant that it would hold before it is used in titration?
For the first one, it's fairly logical. Let's say you found you needed 15.0ml to neutralise it the first time, then 15.1ml the second, then 17.0ml the third time. It should be pretty clear one of those results is an outlier so shouldn't be used. So you should ignore the 17ml as it is clear from your other results that it is likely you may have made an error of some sort - put too much acid in for example.

For the second one: let's say you washed it out with water, when you add the acid, the small amount of water left is mixed in with the acid. Think about how that might effect pH of acid and how that may impact the result.

Been a while since I've done chemistry so appologies if I missed out details but that should be the general jist of what the question is asking.

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