Quality control analysts monitor a trimethylamine cleaning solution by titrating…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Quality control analysts monitor a trimethylamine cleaning solution by titrating 10.00 mL aliquots with 0.600 M perchloric acid at 25 °C. Trimethylamine, (CH3)3N, behaves as a weak base with Kb=7.4×10−5. During one trial, the analyst calculates that the equivalence volume is 7.50 mL of the acid, but, due to a delayed stop, actually dispenses 7.52 mL before recording the pH.
The product specification requires the final pH to be in the range 1.20 – 1.30.
(a) Verify the theoretical volume of 0.600 M HClO4 required to reach the equivalence point for the 10.00 mL aliquot.
(b) Determine the concentration of hydrogen ions present in the titration flask after 7.52 mL of titrant has been added.
(c) Calculate the pH resulting from the analyst’s 0.02 mL overshoot and state whether it falls within the acceptable specification range.
(d) Comment on the sensitivity of post-equivalence pH to small volume delivery errors in this titration, referencing your calculated data.