An impure laboratory standard thought to be benzoic acid (C7H6O2) contaminated with…
CHEMISTRY · Multi-part · A Level · Chemistry · Organic analysis and spectroscopy · Organic analysis and spectroscopy
Problem
An impure laboratory standard thought to be benzoic acid (C7H6O2) contaminated with an inert white powder is subjected to combustion analysis. A 1.500 g portion of the solid is burned completely in excess oxygen, and the products are collected in separate traps. The carbon dioxide trap gains 3.081 g in mass, and the water trap gains 0.541 g.
(a) Show that the observed masses of carbon dioxide and water are stoichiometrically consistent with the complete combustion of a pure sample of benzoic acid.
(b) Determine the mass of benzoic acid present in the 1.500 g portion.
(c) Calculate the percent purity of benzoic acid in the impure standard.
(d) Compute the mass of the inert contaminant present in the sample.
(e) Propose a spectroscopic or chromatographic method that could be used to confirm the identity of the inert contaminant. Explain the principle behind the method and how it would distinguish the contaminant from benzoic acid.