When doing an assay of acidity in Vinegar experiment, why is it a good idea to rinse the buret with NaOH...?

Question

solution, instead of with water, before filling it at the start of the titration?

Answer 1

Glass is basic in nature and could easily hold on to excess protons (if the last time it was used it was used with dil HCl, for example).

If you rinsed with water then the glass would hang onto these excess protons, until you filled your buret with the standardized NaOH solution. Then your NaOH solution would be slightly less strong than expected, and since you are titrating a weak acid your error would be greater, than expected.

So you eliminate this error, by priming the inside of the buret glass with NaOH soultion to make sure that all the protons are gone with the NaOH solution, assuring the NaOH solution added to the buret is the same strength as the standard strength from the reagent bottle.

Answer 2

to prevent dilution of the titrant.

Rinse the buret with NaOH if you're using the Mohr buret and your analyte is the vinegar, but if your titrant is vinegar, then it's not a good idea to rinse the buret with NaOH.

Answer 3

A residue of NaOH in the burret will change the acidity of the acetic acid during the test. You don't want to chance this so don't use sodium hydroxide to rinse with.

Answer 4

Mohr Buret