Q5(c)(ii). Fe₃O₄ in an ore by gravimetry
An ore sample of Fe₃O₄ weighing 1.3155 g was dissolved in HCl, and treated with HNO₃ to convert all iron into Fe³⁺ state. The resulting content was then diluted with water, followed by addition of NH₃ (excess) to precipitate Fe³⁺ into Fe(OH)₃. Ppts were filtered, washed with water and ignited to give the residue of pure Fe₂O₃ weighing 0.7273 g. Calculate % w/w Fe₃O₄ in the ore sample. [Fe₂O₃ = 159.70, Fe₃O₄ = 231.54]
Answer in brief
Gravimetric factor 2 Fe₃O₄/3 Fe₂O₃ = 0.9666; mass of Fe₃O₄ = 0.7030 g, so the ore contains 53.44 % (w/w) Fe₃O₄.
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Coversgravimetric analysisgravimetric factormagnetiteiron oreFe2O3
All parts of Question 5
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- 5(c)(ii) Fe₃O₄ in an ore by gravimetry5 marks