What should be done with any
hanging drops of titrant that remain after running in a titrant from a buret? (A) The drops should be left
hanging from the buret and the conical flask should be carefully moved away. (B) The drops should be absorbed
using a small piece of paper towel. (C) The drops should be added to
the conical flask by gently flicking the nozzle of the buret. (D) The drops should be collected
in a second conical flask. Or (E) the drops should be
collected and reintroduced to the top of the buret.
In order to answer this question,
we need to understand how a buret is used to run a titrant.
A buret is used to run a titrant in
a procedure called a titration. A titration is a quantitative
analytical method used to determine the concentration of an analyte using a known
concentration of a second solution. The buret is clamped upright over a
conical flask. It contains the solution of known
concentration. This solution is called the
titrant. Into the analyte below, the buret
releases a volume of titrant until the reaction is complete and the data can be used
to find the concentration of the analyte.
In order for this quantitative
method to be valid, the volume of known solution reacted must be precisely and
accurately measured using the gradations on the buret. If drops are left hanging on the
end of the buret, the volume reading is compromised. With this in mind, let’s have a
look at our answer choices.
Answer choice (A) suggests that the
conical flask be moved away and the drops left on the buret. These remaining drops would be
included in the volume reading on the buret as it is no longer contained in the
glassware but would not be reacted in the conical flask and thus would alter the
results. Similarly, absorbing the drops
using a paper towel as suggested by answer choice (B) would alter the results.
Answer choice (D) suggests the
drops be collected by a second flask, which would still alter the results by
removing the drops but not reacting them with the analyte. Answer choice (E) suggests the
drops be collected and reintroduced into the top of the buret. While this might not alter the
results, it is an impractical method and this transfer would be difficult.
Answer choice (C) suggests the
drops be added to the conical flask containing the analyte by gently flicking the
nozzle of the buret. This would allow the hanging drops
to fall into the analyte and for the volume reading to be accurate. This would make the volume reading
of the buret valid and the quantitative analysis to be reliable.
Therefore, the correct answer is
(C). After running a titrant from a
buret, any hanging drops that remain should be added to the conical flask by gently
flicking the nozzle of the buret.