What is the best way to minimize the random uncertainty when titrating an acid of unknown strength against a standard solution of sodium hydroxide (ie one of known concentration)?

A.     First standardize the sodium hydroxide solution against a standard solution of a different acid.

B.     Use a pH meter rather than an indicator to determine the equivalence point.

C.     Keep your eye at the same height as the meniscus when reading the burette.

D.     Repeat the titration several times.

D

There was a suggestion that we should have used the phrase “minimize random error” instead of “minimize random uncertainty”. That is a fair point but it didn’t seem to worry the candidates, 75% of whom gave the correct answer.