A 25.00 mL sample of a monoprotic hydrochloric acid solution of unknown concentration…
CHEMISTRY · Multi-part · A Level · Chemistry · Acids and bases · Acids and bases
Problem
A 25.00 mL sample of a monoprotic hydrochloric acid solution of unknown concentration is titrated with 0.1000 M NaOH delivered from a burette. A pH-meter trace shows that the equivalence point is reached after 24.80 mL of NaOH have been added, but the student performing the titration relies solely on the first permanent appearance of a pink color with phenolphthalein, which occurs after only 24.30 mL of NaOH have been added.
(a) Calculate the molarity of the acid that the student would report based on the indicator endpoint.
(b) Determine the percent error in the reported acid molarity relative to the true value obtained from the pH-meter equivalence volume.
(c) Indicate whether the discrepancy introduced by using the indicator is a systematic error or a random error and briefly justify your classification.