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titration (1 Viewer)

lala33

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im doing a redox titration with orange juice to find amount of ascorbic acid for investigating sci and i asked my chem teacher about washing the walls of the conical flask during the titration. she said not to since it will dilute it and that i should rinse and dry my flask before i do everything else.
I thought drying was unnecessary and i could wash the walls since it won't change the concentration. can anyone help or clarify this pls? 🙏
 

indeed

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Hope this helps, lmk if anything doesnt make sense, I agree with mostly what you said though not your teacher
 

Luukas.2

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im doing a redox titration with orange juice to find amount of ascorbic acid for investigating sci and i asked my chem teacher about washing the walls of the conical flask during the titration. she said not to since it will dilute it and that i should rinse and dry my flask before i do everything else.
I thought drying was unnecessary and i could wash the walls since it won't change the concentration. can anyone help or clarify this pls? 🙏
Your teacher is 100% correct that adding water through washing walls and using a wet conical flask will dilute the analyte solution.

You are 100% correct that this does not matter so long as the chemical amount (moles) of analyte does not change. In effect, you are finding the concentration in the 25.00 mL solution that was delivered to the conical flask from the pipette, and so the subsequent dilution does not alter the accuracy of your results.

Where your teacher is seriously misleading you is that washing down the walls of the CF is good / desirable technique (so that any splashed residue is included in the measurement of the end point) and, in fact, not washing the walls is introducing a random-in-size but systematic-in-effect error into the experiment that decreases accuracy.

PS: Ascorbic acid can be analysed by both redox and acid-base titrations... make sure you are describing whichever you are doing correctly. :)
 

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