Would my calculated molarity of HOAc in vinegar be too high, low, or unchanged if

Question

a) i forgot to rinse wet buret with vinegar
b)delivered vinegar into a wet flask
c)used a buret with a broken tip

Any help please!!!

Answer 1

I assume from the problem that you have used vinegar as the titrant and a primary standard OR the know molarity of a base such as NaOH.
HOAc + NaOH ==> H2OP + NaAc.

moles NaOH = L x M = ??
moles HOAc = samae
M HOAc = moles HOAc/L HOAc.
a) So if you did not rinse the buret with HOAc before using it and the buret was wet, then you must add MORE volume (it will take a higher volume because some of what you are adding from the buret is water) so the M will be too low (the denominator is too large).
b. Delivering HOAc into a wet flask, along with the base, will have no effect. That is because the water contains no moles of either base or acid. My students always got confused with that answer and they kept telling me that "we were diluting the HOAc." My answer was, "Tha't right, and we are diluting the base by the same amount."
c. There is no definitive answer for (c) because there are several scenarios; however, the best guess is that we would overshoot the end point which means L HOAc is too high which makes M HOAc too low. But if you were very careful, did not allow a full drop to form before it fell into the titrating flask but allowed just a small amount out of the broken tip before washing it off OR better touching the tip to the titrating flask, I think you could get a good titration and the M HOAc should be ok.