inshm2016 Posted January 31, 2016 Report Share Posted January 31, 2016 I have read a lot that Vitamin C is very soluble in water. But how is that possible if it is a weak acid? Shouldn't it only partially dissociate in water? The thing is, I carried out a titration to determine concentration of Vitamin C. Theoretical value was 0.06 moldm^-3 while my experimental was 0.05. Could an error be that ascorbic acid does not fully dissociate into water? Reply Link to post Share on other sites More sharing options...
Guziec Posted January 31, 2016 Report Share Posted January 31, 2016 (edited) Dissolving in water doesn't necessarily mean that all of the molecules dissolved do dissociate from what I know. Edited January 31, 2016 by Guziec Reply Link to post Share on other sites More sharing options...
kw0573 Posted January 31, 2016 Report Share Posted January 31, 2016 dissolving = breaking intermolecular bonds (in this case, hydrogen bonding, van der waals forces)dissociate / acid behaviour = breaking intramolecular bonds (bonds inside a molecule itself, in this case one of the OH bonds).To calculate theoretical values for your lab, you need the Ka (or pKa) for vitamin C. Reply Link to post Share on other sites More sharing options...
inshm2016 Posted January 31, 2016 Author Report Share Posted January 31, 2016 dissolving = breaking intermolecular bonds (in this case, hydrogen bonding, van der waals forces)dissociate / acid behaviour = breaking intramolecular bonds (bonds inside a molecule itself, in this case one of the OH bonds).To calculate theoretical values for your lab, you need the Ka (or pKa) for vitamin C.What I did was add a specific mass of ascorbic acid powder to 500 ml of water. I calculated the concentration by finding the amount of moles of ascorbic acid and dividing by 0.5 dm^3. And this was my theoretical concentration. I then calculated the experimental and this was less.This has nothing to do with dissociation, right? Reply Link to post Share on other sites More sharing options...
kw0573 Posted January 31, 2016 Report Share Posted January 31, 2016 (edited) Yes the pKa has no effect on volume of base needed, but it does affect the pH. If everything is calibrated / measured very accurately and precisely, there shouldn't be a >10% difference in concentration. Edited January 31, 2016 by kw0573 Reply Link to post Share on other sites More sharing options...
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