Answer Happy

Practice Questions Page 9. 1- A 0.5962 g sample of iron ore is dissolved in perchloric acid (HCIO4). All iron present is oxidized to Fe¹*. The solution is filtered to remove solid matrix materials and made basic with addition of ammonium hydroxide. The iron precipitates as the Fe(OH)3 xH₂O gel. The precipitate is collected in a cistern crucible and ignited to produce Fe2O3. a) Why is the solution filtered after perchloric acid dissolution? -To remove insoluble matrix material (like silica, alumina, etc.) b) Why rinse with ammonium hydroxide solution? To avoid peptization or loss of precipitate. Ammonium hydroxide is a volatile electrolyte. c) Why use a desiccator during cooling? To avoid weight gain by adsorption of atmospheric water d) What is the wt. % of iron in the sample if the analysis produced 0.3210 g Fe2Os? (37.66%) 2 Fe³+ (aq) + 3 OH Fe₂Os (s) 3/2 H₂(g) 0.3210 g