I was never able to meet up with my lab partner this time to compare our reports. There's also no SI for this 5 credit course and the tutors have been scant.
Just looking for some insight into the post lab questions about
-using known base to titrate an unknown acid,
and the prelabs about
-water hardness and spk.
will post what I have so far in a minute
1) What was the purpose of the phenolphtahlein? Could you have performed the titration without the pheno?
THe phonlph was used to indicate when solution changes from acidic to basic. We would need to take many more pH increments of added known base without this color-changing indicatorto show proximity to the equivalence point
2) Did the equiv point ioccur at the same Ph as part 1 (known acid known base) (NaOH + HCl in part 1, unknown HA and NaOH in part 2 which was pH 7.33 at equivalence))
No, weak acids and strong bases will have a more basic equivalnce point than strong aacids with strong bases, which dissociate completely. conversely, weak bases with strong acids will have a more acidic equivalnce point.
3) Stock solution prepared and labaled incorrectly. Labeled HCl 0.200 M was actually 0.250 M.
The base would appear more acidic atequivalence, skewing the numbers to a more strong concentration o base than it should.
4) Student conducts experiment, mistakenly calibrate the pH meter to pH 8 buffer instead of pH 7. The pH meter reasdings were resultantly too low.
a) The equivalence pont would appear to be higher pH than actual. It would still take the same amount to reach it, though.
b) Would this effect ehe xperimentally determined value of pKa?
PRELAB
1) EDTA is a chelating agent. In your own words:
Chelating agents bind multiple cations making them useful in measureing water hardness
2) pH 10 buffer solution of aq NH3 and NH4Cl which species is the weak base with is the conjugate acid
acqueous ammonia is weak base, ammonium chloride is the conjugate base
3) For what reason are we buffering the solution to be basic? What would happen to the structure of EDTA wthout a buffer?
4) Use the internet to lookup area grains per gallon of water hardness convert to mg/L
found this