Titration question


by ASidd
Tags: titration
ASidd
ASidd is offline
#1
Mar1-13, 07:20 AM
P: 73
Okay this maybe a silly question but I had to ask.

In school we are making standard solution to perform a titration. To do this we measured in grams a sample of oxalic acid and mixed in water and then made the solution up to mark in a volumetric flask.

When I did my titration; as I was mixing my oxalic acid in water I realized there was a tiny very tiny piece of hair in it. I have no idea how it got there. It was really small BUT our teacher said that we had to be sure to measure the mass of the acid used very accurately.
So my question is how much can a tiny piece of hair affect the mass??

Also When I had made my solution up to mark in the volumetric flask, I transferred it into a bottle using a funnel which was slightly wet. It probably had 3-4 droplets of water in it.

Can a few droplets cause significant changes in volume? Would it be better to start again and make a new solution?
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epenguin
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#2
Mar1-13, 09:01 AM
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Ideally and if you have the time and possibility, then yes, do it again. Also for the sake of your morale. It will go better the second time.

Then I do not think the errors are very great. There is probably nothing soluble in the hair to give greater than your inevitable % of error; the droplets in the filter might be more but if you filtered 100 or 200 ml I doubt they make measurable difference. Ideally again keep your bad solution and titrate that as well as the good new solution, so then you actually see. But if there are any differences this is still not significant unless you titrate the same solution say 3 times and see what the errors, the variation between the same titrations, are.

Ideally.
Borek
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#3
Mar1-13, 11:25 AM
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Wet funnel shouldn't matter, as long as the droplets didn't contain anything that could react with your titrant (or titrated substance). You should rinse the funnel with a distilled water after transferring the solution, to make sure none of your substance was left there (which means you should collect rinsing water!). You were diluting it to the mark, so the final volume is under control.


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